Local Climate Baseline. 9A.1 Introduction

Transcription

1 9A Local Climate Baseline 9A.1 Introduction Meteorological data (including temperature, rainfall, wind speed and direction, relative humidity and evaporation) has been collected for the purposes of the Project for a number of years. This annex presents an overview of the baseline conditions of key aspects of local climate (wind, rainfall, fog and mist) and then presents a detailed Baseline Climate Report, prepared on behalf of the Project in January 2009 (1). 9A.2 Local Climate Overview The climate in Guinea is governed by the position of the Inter-Tropical Convergence Zone (ITCZ), a large zone of low pressure caused by enhanced heating from a directly overhead sun. The ITCZ circles the Earth and marks the latitude at which solar heating of the Earth s surface is locally greatest at any given time of year. The sun s energy ensures that the surface air at the ITCZ is locally hotter than the air to the north and south, causing air to rise. Thus at Simandou the time of year and the position of the ITCZ dictate the predominant climate conditions. With the hot dry Sahara to the north and the warm, moist areas towards the Gulf of Guinea in the south the overall effects are for regional monsoons and Harmattan winds from the Sahara during the dry season. Within this overall context, there will be aspects of the microclimate for individual locations on and around the ridge where the ridge itself exerts an influence. It is these subtle deviations from the overall climate that have the greatest potential to be at risk of modification by the proposed mining activities. The specific climate of the Simandou ridge is undoubtedly influenced and modified by the presence of the mountain. The ridge is aligned in a north-south direction and therefore acts as a barrier to winds with a significant westerly or easterly component. In particular, this means the moist southwesterly winds of the wet season and the dry northeasterly winds of the dry season, known locally as the Harmattan wind. The ridge itself will induce local wind circulations, for which there are a number of possible mechanisms. The ridge can also be reasonably expected to perturb the regional rainfall patterns and influence fog formation. The meteorological conditions follow a clear seasonal pattern, with the wet season most evident in August and September, and the dry season most evident in January; the monitoring of relative humidity and rainfall clearly follow this trend year on year. There is little variation between the monitoring sites (See Figure 9.1 in the Local Climate chapter), indicating that relative humidity and rainfall are regional phenomena and less affected by local circumstances. In addition, temperature also follows this seasonal trend, with the highest ambient temperatures during the dry season. 9A.3 Wind Speed and Direction Wind direction shows a seasonal variation in line with the cycle of wet and dry seasons caused by the movement of the ITCZ. Thus, in this part of Guinea, the predominant direction of the surface wind is governed by the ITCZ, as shown in Figure 9A.1. (1) (January 2009), Baseline Climate Report. Simandou SEIA Volume I Mine Annex 9A 9A-1

2 Figure 9A.1 Location of the ITCZ (labelled ITD) over West Africa in January (left) and July (right) (Oke 1977 reproduced in Fullwood and Johnson 2008). In the dry season the ITCZ lies to the south of the study area, with northeasterly winds blowing towards it across Simandou. In the wet season, the surface position of the ITCZ moves to the north, resulting in southwesterly wind, at least in the lower atmosphere. The vertical structure of the ITCZ is such that in the air mass, often as low as the summit of the Simandou Range, winds remain northeasterly for much of the time. The additional influences or triggers such as convection, easterly waves and topography are superimposed on this fundamental mechanism. The height and shape of the Simandou Range also influence the microclimate and cause localised wind channelling and this can explain the small amount of variation between the monitoring sites within the general trend. For example, the leeward (sheltered) side of the ridge may experience the effects of a wind rotor where the wind direction becomes reversed on the leeward side of the ridge and blows gently back up the slope in the opposite direction to the wind aloft. This up-slope airflow, combined with moisture from the forest below, contributes to the formation of the fog frequently observed on the western slopes of the Simandou ridge. Overall, these localised effects will have little effect on impacts as these are more dependent upon macro-scale effects. Figure 9A.2 shows the annual wind roses for Dabatani, Kerouane, Mandou and Mafindou. Wind speeds at all locations are relatively light compared to more temperate areas of the world, and this is to be expected given the tropical setting. As is typical in a tropical setting, wind speeds at all locations are relatively light. Wind speed measurements at the higher Dabatini site show elevated wind speeds in comparison to locations at lower altitude such as Mandou and Mafindou. The lighter winds recorded at Mandou is likely the result of influence of the Simandou Range which shelters this location from higher wind speeds. During the dry season in more northeasterly winds, the wind rotor formed on the lee side of the Simandou Range would account for a reversed light southwesterly wind, whilst during the wet season the winds would be from the southwest. The wind speeds recorded at Mafindou are lower than expected given the station s elevated location in comparison to the surrounding terrain. The lower measured wind speeds may be due to the valley to the west of Mafindou which would funnel wind around the elevated position in which Mafindou is located during northeast winds. When the wind is from the southwest, Mafindou is likely protected by the Simandou Range 10 km to the west. Simandou SEIA Volume I Mine Annex 9A 9A-2

3 Wind measurements at Dabatani and Kerouane show elevated wind speeds in comparison to more sheltered locations at Mandou and Mafandou. This is a result of the more elevated positions of the monitoring stations. Data collected at Dabatani, indicates a dominant east to north easterly direction, with few occurrences of south west winds. This is probably the result of the location of the monitoring station just to the east of the peak of the Simandou ranges, resulting in greater exposure to the upper level winds that are dominated by the structure of the ITCZ where the winds remain northeasterly for much of the time. Kerouane is situated in an elevated location at the northern end of the Simandou Range, but on a range of hills to the west. This location means that neither the north east winds of the dry season, nor the south west winds of the wet season are blocked by topographic features resulting in the clear dominance of north east and south west winds in the wind rose. Figure 9A.2 Wind roses for Dabatani, Kerouane, Mandou and Mafindou. Adapted from (Fullwood & Johnson, 2008) Dabatani Annual wind rose for June 2004 to May 2005 Kerouane wind rose for 2004 and 2006 combined Mandou wind rose for 2004 and 2005 combined Mafindou wind rose for 2004 and 2005 combined Wind measurements at Mandou and Mafindou indicate that wind speeds in these locations are lighter than at Dabatani and Kerouane. In the case of Mandou, this is likely the result of influence from Simandou range which shelters this location from higher wind speed events. Consideration of Figure 9A.2 indicates that winds are predominantly light and from the south-west throughout the year. It is considered that during the dry season in more north-easterly winds, the wind rotor formed on the lee side of the Simandou Range would account for a reversed light south westerly wind, whilst during the wet season the winds would be of south west. Simandou SEIA Volume I Mine Annex 9A 9A-3

4 9A.4 Rainfall Guinea has a predominantly tropical humid climate (transitioning to a more equatorial climate in the southeast of the country) with a distinct seasonal pattern characterised by rainfall generated by the migration of the ITCZ. The upward displacement of air caused by the ITCZ causes the air to the north and south of the ITCZ to be drawn into this convergence zone and causes heavy rainfall due to the uplift (convection) of moist southwesterly air flows in the areas it passes over as it moves north and south between the tropics during the respective northern and southern hemisphere summers. The ITCZ moves northwards across Guinea from January to July, drawing moist air from the Atlantic Ocean across the country as it proceeds (the southwesterly monsoons). It then moves southwards from August to December during which time the dry northeasterly (Harmattan) winds from the Sahara become more dominant. As a result of this movement, the wet season is longest in the south of the country, lasting up to 10 months in southern provinces such as Nzérékoré. It is shortest in the north, where it usually lasts around five months between May and September, peaking in August. There is a corresponding gradient in annual rainfall totals from north to south across the country, which range from around mm in the drier northeast, to well over mm in parts of the south. This represents a marked decrease in annual rainfall moving inland from the Atlantic coast, where annual totals are in excess of mm. Regional rainfall patterns can also vary due to relief effects, for example due to the uplift of moist southwesterly air flows and corresponding enhancement of rainfall caused by the Fouta Djalon massif in Central Guinea, and the Dorsale Guinéenne in the southeast. This monsoon generates heavy rainfall throughout southeastern Guinea, irrespective of topography. These regional climate effects feed into and drive local climate phenomena, and are sufficient to generally describe the dry and wet season and the majority of regional precipitation events. The Simandou Range has a relatively high average annual rainfall of around mm, with a wet season lasting for around 8 months, from March to October. The wet season is estimated to extend for 230 to 260 days in this part of Guinea, during which rain occurs on around 160 days or more. Data collected in the period 2002 to 2005 at locations on the Simandou ridge show that annual rainfall amounts are in the range up to mm, most of which falls in the wet season, with only 150 to 300 mm falling in the months of January to March. Detailed rainfall contours derived for the mine site are shown in Figure 9A.3. A relationship has been found between annual rainfall and aspect in relation to the North-South Simandou ridge, with higher rainfall to the west of the ridge than to the east. However, no simple relationship was found between annual rainfall and site altitude; the highest rainfall was not on the summits but on the upper west-facing slopes. The rainfall generally has a saw-tooth profile through the year, rising gradually from March to July, peaking in August and falling away from September onwards. Although rainfall predominantly occurs during the wet season, it can also occasionally occur during the dry season. The storms themselves generally have a strong convective characteristic, with short, intense downpours often occurring in the early / late wet season. More prolonged but less intense rainfall is typical for mid-season. Simandou SEIA Volume I Mine Annex 9A 9A-4

5 Figure 9A.3 Beyla daily rainfall (mm) for 2000 to 2005 (Fullwood & Johnson, 2008) 9A.5 Fog and Mist Formation Vegetation variation on the slopes of the Simandou ridge is considered to be the main factor in fog and mist formation. The vegetation on the upper slopes of the Simandou ridge is predominantly grass with wooded grassland on the lower eastern slopes and forest on the lower western slopes. The forest on the lower western slopes tends towards wooded grassland towards the north of Simandou. The variation in vegetation cover between the east and the west of Simandou ridge results in a significant difference in the availability of moisture to the atmosphere. The atmosphere of the surface layer over the forest therefore remains very humid throughout the year. During the dry season, the north east Harmattan wind causes wind rotors on the eastern side of the Simandou ridge to push the humid air above the forest in to the dryer air above resulting in the formation of mist and low cloud. During the wet season, the south west winds push the moist air over the forest up the side of the mountain, again resulting in condensation and the formation of mist and low cloud on the eastern side of the ridge. Consequently, mist and low cloud is observed on the eastern side of the ridge on most mornings of the year. Simandou SEIA Volume I Mine Annex 9A 9A-5

6 BASELINE CLIMATE REPORT January Prepared for: Rio Tinto Iron Ore Atlantic Ltd Corniche Sud Madina Dispensaire rue MA-500 BP 848, Conakry Republic of Guinea, West Africa Prepared by: (A Schlumberger Company) The Pump House Coton Hill Shrewsbury SY1 2DP United Kingdom

7

8 CONTENTS Page 1 INTRODUCTION 1 2 REGIONAL CONTEXT 3 3 INFORMATION SPECIFIC TO THE PROJECT AREA Methodology Results Atmospheric pressure Solar radiation Temperature Wind direction and speed Humidity Evaporation Precipitation Historical climate change Future climate change 20 REFERENCES 21 TABLES 2.1 Rainfall (mm) at stations in south east Guinea Temperatures (degrees Celsius) at stations in south east Guinea Summary data on atmospheric pressure (mbar) Summary data on solar radiation (MJ m-2 day-1) Summary data on temperature (degrees Celsius) Summary data on wind speed (m s1) Summary data on relative humidity (% saturation) Summary data on evaporation (mm) Summary data on rainfall (mm) Maximum short-term rainfall depths and intensities recorded at the project site,

9 Contents FIGURES After page 2.1 Mean annual rainfall in Guinea, Mean annual rainfall in south east Guinea, Meteorological monitoring network and estimated mean annual rainfall in the project area, Relationship between altitude and average atmospheric pressure at the project site Atmospheric pressure at Dabatini, August 2004-July Diurnal variation in atmospheric pressure on Pic de Fon, 14 August Solar radiation at Dabatini, August 2004-July Diurnal variation in solar radiation on clear and cloudy days at Dabatini Monthly mean solar radiation, August 2007-February Air temperature at Dabatini, August 2004-July Diurnal variation in temperature on clear and cloudy days at Dabatini Relationship between temperature and altitude on Pic de Fon Wind direction and speed at Dabatini, July 2004-June Wind direction and speed on Pic de Oueleba, July 2007-February Wind direction and speed at Mafindou, May 2004-April Wind direction and speed at Mandou, May 2004-April Relative humidity at Dabatini, June 2004-May Diurnal variation in relative humidity in the wet and dry seasons at Dabatini Daily potential evapotranspiration and open water evaporation at Dabatini, Occurrence of fog at Canga East and Oueleba camps Rainfall transects, July 2007 January Monthly and annual rainfall at Canga East, Diurnal variation in rainfall on Pic de Fon Thunderstorms recorded at Canga East, Trends in temperature and rainfall at Beyla, Kerouane and Kissidougou Trends in temperature and rainfall at Macenta and Nzerekore 20 ANNEXES A Potential climatological impacts of mining in the Simandou Hills. Phase 1: Current climate and mechanisms: Final Report. 14 March Met Office, UK B List of RTIOAL weather stations and rain gauges C Methodology used for estimation of potential evapotranspiration and open water evaporation D Climatological Study of Simandou Hills Area of Guinea West Africa Climate Predictions. Review, 9 January 2008, Met Office, UK

10 1 1 INTRODUCTION This report presents the baseline regional and local climate and meteorology of the project site. Data have been provided by the Département National de la Météorologie (DNM) in Conakry for climate stations in the region. These data have been used to characterise the climatic setting of south east Guinea. For the characterisation of the climate and its variability at the project site meteorological data are presented which have been measured as part of a meteorological monitoring programme at the site. A particular concern of the project is that by lowering the altitude of the ridge at Pic de Fon and at Oueleba, changes may be caused in rainfall and other meteorological variables which may have additional environmental effects. To address this concern a study has been made of rainfall at the project site and its relationship to altitude and aspect (east vs west facing slopes). The study has involved empirical measurements of rainfall under pre-project baseline conditions and a numerical modelling study. The UK Met Office (UKMO), assisted by the DNM, has undertaken the modelling study. The UKMO has produced a number of reports. The first of these reports (the Phase 1 report) characterises the regional and local climate, establishes the dominant rainfall mechanisms, assesses the significance of orographic rainfall and describes the meteorological mechanisms giving rise to the patterns and is presented herein (Annex A). The modelling work will be reported as part of the Environmental Impact Assessment. The following text draws on the UKMO s Phase 1 report. Meteorological data are presented in this section to illustrate and quantify aspects of the climate at the site. The reader is referred to Annex A for a more detailed description of the meteorological mechanisms.

11 2 Introduction THIS PAGE HAS BEEN LEFT BLANK INTENTIONALLY

12 3 2 REGIONAL CONTEXT This section gives a brief overview of the regional climatic context. Meteorological conditions at the project site are described in Section 3. The climate of south east Guinea, and of the project site, is seasonal humid tropical and is dominated by the West African Monsoon. Figure 2.1 shows the generalised distribution of mean annual rainfall across Guinea, taken from Barry and Sivakumar (1997). Figure 2.2 focuses on south east Guinea and takes account of data from the project area. The Simandou range modifies the regional distribution of rainfall and other meteorological variables. For example, there are steep east-west gradients in rainfall across the range. Temperatures at elevation will be lower than those on the plain to the east and west of the range (see below). In simple terms the climate of Guinea is dominated by phenomena that are driven the interaction of (a) the seasonal migration of the overhead sun and zone of maximum radiation and heating northwards during January to July and southwards during August to December, (b) related seasonal changes in the distribution of subtropical high pressure systems over the Sahara Desert and the Atlantic ocean to the south. Large scale uplift of air is associated with the zone of maximum heating, creating a migrating latitudinal zone of low pressure into which converge dry surface winds from the north east and moist surface winds from south east originating from the zones of high pressure over the Sahara and Atlantic ocean respectively. This zone is often called the Inter-Tropical Convergence Zone (ITCZ) and is characterised as a zone of instability and increased rainfall resulting from widespread uplift (convection) of moist air. In December the ITCZ is at its southern-most average position of 5 o N. At this time dry north easterly winds dominate over Guinea, creating dry season conditions. The ITCZ migrates northward passing over southern Guinea between February and May. The most northerly position of the ITCZ is on average 20 o N and is reached in July-August. The ITCZ then migrates southwards, passing a second time over Guinea between August and September/October. Because air to the south of the ITCZ is moist, rainfall over Guinea, and the project area, is seasonal and monsoonal. The rainy season is longest in the south of the country (9-10 months in Nzérékoré/Macenta) and shortest (5 months) in the north. The rainy season at the project site lasts approximately eight months, from March to October. The dry season lasts from November to February. Although a clear distinction is made here between the rainy season and the dry season, rainfall can occur in the dry season. Approximately 90-95% of annual rainfall occurs in the wet season in south east Guinea. Tables 2.1 and 2.2 presents monthly mean rainfall and temperatures at DNM weather stations in south east Guinea. These data are portrayed on Figure 2.2. They show the seasonal distribution of rainfall and temperature. The highest temperatures occur in the early part of the year. Temperatures are lower in the middle of the year, even though the sun is overhead, because of the increased cloud cover during the monsoon period.

13 4 Regional context A more detailed discussion of the regional climatic context of the project and the meteorological mechanisms giving rise to it can be found in Annex A. Table 2.1 Rainfall (mm) at stations in south east Guinea Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Beyla Monthly Mean Monthly max Monthly min Daily Max n Kerouane Monthly Mean Monthly max Monthly min Daily Max n Kissidougou Monthly Mean Monthly max Monthly min Daily Max n Nzérékoré Monthly Mean Monthly max Monthly min Daily Max n Macenta Monthly Mean Monthly max Monthly min Daily Max n Source: Direction Nationale de la Météorologie de Guinée n = Lumber of months of record

14 Regional context 5 Table 2.2 Temperatures (degrees Celsius) at stations in south east Guinea Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Beyla Monthly Mean Daily Max Daily Min Kerouane Monthly Mean Daily Max Daily Min Kissidougou Monthly Mean Daily Max Daily Min Nzérékoré Monthly Mean Daily Max Daily Min Macenta Monthly Mean Daily Max Daily Min Source: Direction Nationale de la Météorologie de Guinée

15 6 Regional context THIS PAGE HAS BEEN LEFT BLANK INTENTIONALLY

16 7 3 INFORMATION SPECIFIC TO THE PROJECT AREA 3.1 Methodology A network of three automatic weather stations was installed by RTIOAL in the project area in December These stations are arranged in an east-west transect across the range: at the base of the range on the east and west sides (at altitude 830 m at Mafindou and at 710 m at Mandou, respectively), and on the crest of the range at 1650 m at Dabatini. A fourth station was also installed on the crest of the range at 1430 m at Kerouane, 80 km to the north. The three stations in the project area were supplemented in July 2007 by two additional weather stations which were installed on the Pic de Oueleba (1330 m) and at a location called Fokou West (at 810 m) in a clearing in the forest on the south west slope of the range. Powered by solar panels, the stations record rainfall, temperature, humidity, wind speed and direction, solar radiation and pressure at 30 minute intervals. Not all parameters have been measured continuously at each station. For example, Mafindou and Mandou stations were not initially equipped to measure radiation or humidity. In addition, there are some gaps in the record owing to equipment malfunction. However, since July 2007 all stations have been recording all the above parameters. Annex C provides details of the locations of the weather stations. In addition to the weather stations a number of automatic rain gauges were installed in late 2006/early 2007 to provide detailed information on rainfall in different parts of the project site. Their locations were chosen so as to form additional east-west transects across the Simandou range to the north and south of the Mafindou-Dabatini-Mandou transect and at the same time to provide rainfall data for catchments in which streamflow is monitored. Powered by batteries, the automatic rain gauges record rainfall depth at 30 minute intervals, the same as the weather stations.

17 8 Information specific to the project area In addition, during 2007 a number of manual rain gauges were installed in villages surrounding the Simandou range to provide information on rainfall at the margins of the project area. The manual rain gauges are read twice a day at 08:00 hours and at 16:00 hours. At the same times the observers record the occurrence of fog and thunder storms since the previous observation. Annex C provides details of the locations and status of the rain gauges. Figure 3.1 shows the locations of the weather stations and rain gauges. All meteorological data are stored in a digital database. While climate data have been collected at several stations at different locations at the project site, the proposed mine will be developed on the top of the Pic de Fon range and on the top of Oueleba. For this reason, emphasis is placed in this section on presenting baseline climate information from the weather stations at Dabatini and Oueleba. The following text presents graphs and tables of data measured in the project area to illustrate, characterise and make general statements about the climate and meteorology of the project site. The order of presentation is: atmospheric pressure, solar radiation, temperature, wind direction and speed, humidity, evaporation and precipitation. Lastly, evidence of climatic change in the project area is presented. 3.2 Results Atmospheric pressure Since the Simandou range at the project site varies from about 700 m asl at the base of the mountain to 1656 m on the Pic de Fon, atmospheric pressure also varies significantly, decreasing from 935 mbar at 700 m to 838 mbar at 1650 m. Figure 3.2 shows that pressure decreases linearly with altitude by 10.2 mbar for every 100 m increase in elevation. If the average altitude of the Pic de Fon ridge is assumed to be 1400 m the average pressure on the ridge top is 864 mbar. On Oueleba the average pressure is 870 mbar. As is typical of tropical regions there is only a small seasonal variation in atmospheric pressure. Figure 3.3 shows the monthly and daily variation in pressure recorded at Dabatini. Owing to malfunction of the station the period August 2004 to July 2005 is the only 12-month period of continuous records. There is a seasonal variation in mean pressure of just 2 mbar between a high of nearly 840 mbar in July-August to a low of nearly 838 mbar in February. Pressure varies from day to day throughout the year, but rarely by more than 3 mbar. The seasonal variation in pressure is related to that of temperature. Figure 3.3 shows that the period of highest pressure (the wet season) coincides with the period of lowest temperature (which itself is related to cloud cover and high humidity) and the period of lowest pressure (the dry season) coincides with the period of highest temperature. There is also a diurnal variation in pressure at the site that is typical of the tropics. Figure 3.4 shows the diurnal pressure wave at Dabatini has an amplitude of about 2 mbar. Maxima occur between 08:00 and 14:00 hours and again between 22:00 and 24:00 hours. Minima occur around 04:00 hours and 18:00 hours. The cause is not known for certain, but is likely to be related to the daily rhythm of heating and cooling. Table 3.1 presents summary data on atmospheric pressure recorded at the automatic weather stations.

18 Information specific to the project area 9 Table 3.1 Summary data on atmospheric pressure (mbar) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Dabatini automatic weather station, 1650 m (Dec Dec 2008) Monthly mean Daily max Daily min n Fokou West automatic weather station, 810 m (Jul Dec 2008) Monthly mean Daily max Daily min n Mafindou automatic weather station, 830 m (Feb Dec 2008) Monthly mean Daily max Daily min n Mandou automatic weather station, 710 m (Feb Dec 2008) Monthly mean Daily max Daily min n Oueleba automatic weather station, 1330 m (Aug Dec 2008) Monthly mean Daily max Daily min n n = number of months of record Solar radiation Figure 3.5 shows the monthly and daily variation in solar radiation recorded at Dabatini weather station over the 12-month period from August 2004 to July Monthly mean radiation varies from MJ m -2 day -1 in the wet season to MJ m -2 day -1 in the dry season. There is considerable day to day variation in radiation throughout the year depending on cloudiness, particularly at the start and end of the wet season. There is considerable variation in solar radiation over the course of a day at the project site. Figure 3.6 shows the radiation received on a typical day in the wet season (22 July 2007) and in the dry season (15 January 2008). During the wet season cloud cover and fog significantly reduce solar radiation levels from those on a clear day. Figure 3.7 shows the monthly mean radiation received by all the meteorological stations between August 2007 and February Solar radiation is relatively low at all stations in the wet season and increases towards the dry season. Dabatini and Fokou West receive the lowest radiation in the wet season owing to the frequent occurrence of cloud and fog on the western slopes of the range. The Pic de Oueleba is less prone to low cloud and fog and receives more radiation than Dabatini. Mafindou on the east side of the range receives the most radiation in the wet season. Mandou on the west side receives similar amounts of radiation to Dabatini indicating greater cloud cover on the west side then on the east. Table 3.2 presents summary data on solar radiation recorded at the automatic weather stations.

19 10 Information specific to the project area Table 3.2 Summary data on solar radiation (MJ m -2 day -1 ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Dabatini automatic weather station (Dec Dec2008) Monthly mean Daily max Daily min n Fokou West automatic weather station (Jul Dec 2008) Monthly mean Daily max Daily min n Mafindou automatic weather station (Aug 2007 Dec 2008) Monthly mean Daily max Daily min n Mandou automatic weather station (Sept Dec 2008) Monthly mean Daily max Daily min n Oueleba automatic weather station (Aug Dec 2008) Monthly mean Daily max Daily min n n = number of months of record Temperature Figure 3.8 shows the seasonal variation in mean, maximum and minimum temperatures on Dabatini for the 12-month period from August 2004 to July Although Figure 3.8 is for a particular year the patterns shown are representative of other years. Air temperature varies seasonally and from day to day depending on cloudiness, wind speed and humidity. On Dabatini there is only a 4 o C difference in monthly mean temperature between the mean wet season (July-August) temperature of about 16 o C and the dry season (February-March) temperature of about 20 o C. Temperatures in July- August are limited by cloudy skies which limit heating, and are highest in the dry season when solar radiation levels are high. The daily range between maximum and minimum temperatures is least in the cloudy wet season and greatest in the dry season when night time skies are clear causing lower night time temperatures through greater loss of heat from the atmosphere. Temperature varies diurnally, principally in response to cloudiness, humidity and wind speed. Figure 3.9 shows the diurnal variations in temperature at Dabatini on typical days in the wet season (22 July 2007) and in the dry season (15 January 2008). The diurnal variation in solar radiation for these same days is shown in Figure July was a very cloudy day and temperatures stayed virtually constant at about o C. On the other hand, 15 January 2008 was cloudless and temperatures peaked at about 24 o C around 15:00 hours. Minimum temperature (17.5 o C) occurred at 07:00 hours just before sun rise, giving a daily range of 6.5 o C.

20 Information specific to the project area 11 There is an inverse relationship between temperature and altitude. Figure 3.10 shows that mean, maximum and minimum temperatures decrease with altitude on the Pic de Fon. It is expected that similar relationships exist for Oueleba. Table 3.3 presents summary data on temperature recorded at the automatic weather stations. Table 3.3 Summary data on temperature (degrees Celsius) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Dabatini automatic weather station (Dec Dec 2008) Monthly mean Daily max Daily min n Fokou West automatic weather station (Jul Dec 2008) Monthly mean Daily max Daily min n Mafindou automatic weather station (Jan 2002 Dec 2008) Monthly mean Daily max Daily min n Mandou automatic weather station (Dec Dec 2008) Monthly mean Daily max Daily min n Oueleba automatic weather station (Aug Dec 2008) Monthly mean Daily max Daily min n n = number of months of record Wind direction and speed Wind direction and speed vary significantly over the course of the year depending on site and elevation. Figures 3.11 to 3.14 show wind roses for Dabatini, Oueleba, Mafindou and Mandou respectively. Wind speeds are higher on the more exposed ridges of Pic de Fon and Oueleba than at the base of the mountains. In July and August Dabatini experiences monsoon winds from the south west. Wind speeds exceed 10 m s 1. Figure 3.12 indicates that on Oueleba in July and August 2007 the wind direction was from the west. In September and October (2004) at Dabatini there was an abrupt change in wind direction to an easterly airflow which was maintained until December During these months the depth of the monsoon wind layer probably reduces and is insufficient to reach the elevation of Dabatini. At these times Dabatini experiences easterly winds which overlie the surface winds and blows, with some variation, all the year round. The same change in wind direction was experienced on Oueleba in September-October 2007, although the winds were lighter and initially from the south east. In January-February 2004 the wind at Dabatini veers to the north east and becomes stronger. This is the Harmattan wind which blows from the Sahara. In January-February 2007 at Oueleba wind continued to blow from the east. At Dabatini from March through to June 2004 the harmattan weakened and the easterly wind re-established itself.

21 12 Information specific to the project area The above pattern is somewhat modified at the low stations on the east and west stations by the north-south oriented orography which tends to enhance the northerly or southerly components of winds (Figures 3.12 and 3.14). The main exception is at Mafindou on the eastern side of the range when the harmattan wind blows from the north east in January- February. Wind direction at Mandou is more variable, perhaps indicating the presence of wind rotors, as explained in Annex A. Daily mean wind speeds are much lower at Mafindou and Mandou than at Dabatini, only exceeding 2 m/s during the early part of the wet season (April-May), the height of the wet season (July-August) and at the height of the dry season (January). Table 3.4 lists summary data on wind speed recorded at the automatic weather stations. It is worth noting that Dabatini weather station (a 9 m high tripod) was blown over during a storm on 19 August Although unrecorded, that wind speed likely exceeded the maximum of 32 m/s so far recorded. Table 3.4 Summary data on wind speed (m s 1 ) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Dabatini automatic weather station (Dec Dec 2008) Monthly mean Daily max Daily min n Fokou West automatic weather station (Jul Dec 2008) Monthly mean Daily max Daily min n Mafindou automatic weather station (Feb Dec 2008) Monthly mean Daily max Daily min n Mandou automatic weather station (Feb Dec 2008) Monthly mean Daily max Daily min n Oueleba automatic weather station (Jul Dec 2008) Monthly mean Daily max Daily min n n = number of months of record. The daily maximum wind speed is an instantaneous maximum Humidity The water vapour content of the air at the project site, as measured by relative humidity, is strongly related to the provenance of the wind. North easterly and easterly winds bring drier air. Southerly and south westerly winds bring air of higher humidity. There is a strong seasonal variation in humidity (and rainfall) which is closely related to the seasonal variation in wind direction (see above).

22 Information specific to the project area 13 Figure 3.15 shows the seasonal and day to day variability in relative humidity over the period June 2004 to May During the wet season the air is close to saturation for much of the time, with limited day to day variability. With the onset of the dry season and the variability of wind direction and provenance (see above), humidity becomes more variable. Daily mean relative humidity at the height of the dry season reaches lows of around 20-30%, but can reach maxima of 80-95% during incursions of moist air from the south. Relative humidity varies diurnally in response to diurnal temperature variations. Figure 3.16 shows the diurnal variation in relative humidity for typical days in the wet and dry season. During 22 July 2007 the air remained close to saturation throughout the 24 hour period. In contrast, on 15 January 2008 the relative humidity varied from 50-60% during the night and morning when temperatures would have been relatively low, falling after 11:00 hours as temperatures rose to around 30-35% during the afternoon and evening. That the relative humidity remained low after 19:00 reflects the low moisture content of the air. Table 3.5 presents summary data on relative humidity recorded at the automatic weather stations. Table 3.5 Summary data on relative humidity (% saturation) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Dabatini automatic weather station (Nov Dec 2008) Monthly mean Daily max Daily min n Fokou West automatic weather station (Aug Dec 2008) Monthly mean Daily max Daily min n Mafindou automatic weather station (Aug Dec 2008) Monthly mean Daily max Daily min n Mandou automatic weather station (Sep Dec 2008) Monthly mean Daily max Daily min n Oueleba automatic weather station (Jul Dec 2008) Monthly mean Daily max Daily min n n = number of months of record.

23 14 Information specific to the project area Evaporation Evaporation occurs from open water surfaces, from bare ground surfaces, from water intercepted by vegetation and from plant stomata (called evapotranspiration). Evaporation may be measured directly using an evaporation pan, or estimated indirectly by calculation using meteorological data. Direct measurements of evaporation have not been made at the project site. Instead reliance has been placed on estimation of evaporation using meteorological data recorded by the automatic weather stations. Two indices of estimated evaporation are presented here: Reference crop evapotranspiration ET o (the potential rate of evaporation from short vegetation via plant stomata, calculated from meteorological data, assuming that the vegetation is not short of water and transpires at a maximum rate which is controlled by meteorological factors, specifically the energy provided by solar radiation and aerodynamic characteristics, e.g. wind speed). Evaporation from an open water surface E o (this is also calculated from and is assumed to be controlled by meteorological factors). ET o has been calculated using the Penman-Monteith method (Allen et al, 1998). E o has been calculated using the Penman (1948) equation. Both rely on meteorological data from the meteorological stations. Details of the methods are given in Annex D. Figure 3.17 shows the daily variation in ET o and E o calculated using data from Dabatini automatic weather station. Daily values of PET range from maxima of 5-8 mmd -1 in the dry season to 1-2 mm d -1 in the wet season. Estimates of open water evaporation are always larger than estimates of potential evapotranspiration because of the absence in the methodology of estimated stomatal resistance to evaporation. Daily values of E o in the dry season reach large values of mm d -1 (250 mm per month). The high wind speeds recorded at Dabatini are responsible for this. Table 3.6 presents summary data on evaporation calculated using data recorded at the automatic weather stations.

24 Information specific to the project area 15 Table 3.6 Summary data on evaporation (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Fokou West automatic weather station (Aug Dec 2008) Mth Mean ET o Mth mean E o Daily mean ET o Daily mean E o n Dabatini automatic weather station (Dec Dec 2008) Mth mean ET o Mth mean E o Daily mean ET o Daily mean E o n Mafindou automatic weather station (Dec Dec 2008) Mth mean ET o Mth mean E o Daily mean ET o Daily mean E o n Mandou automatic weather station (Dec Dec 2008) Mth mean ET o Mth mean E o Daily mean ET o Daily mean E o n Oueleba automatic weather station (Jul 2007 Dec 2008) Mth mean ET o Mth mean E o Daily mean ET o Daily mean E o n n = number of months of record Precipitation This section considers forms of precipitation at the project site, rainfall mechanisms, rainfall distribution, rainfall variability, diurnal variability, rainfall intensity and the occurrence of thunderstorms. Forms of precipitation Precipitation at the project site occurs as fog, hail and as rainfall. The occurrence of fog is related to the humidity and temperature of the air. Fog forms when the temperature of air falls to the dew point temperature. At the dew point temperature the air is saturated with water vapour and any further drop in temperature causes water vapour to condense into fine water droplets. There are no systematic observations of fog on the Pic de Fon or Oueleba mountains. In May 2007 observers of the manual rain gauges in the villages surrounding the range were asked to keep a record of the occurrence of fog between the hours of 16:00 and 08:00 (the times at which they made rainfall observations). Figure 3.18 shows the monthly occurrence of fog at Canga East and Oueleba camps during 2007, the period for which information is available. The record at Oueleba is incomplete. However, Figure 3.18 suggests that fog is more frequent at Oueleba than at Canga East.

25 16 Information specific to the project area Fog is a common phenomenon on the west side of the Pic de Fon range and on Oueleba on most mornings during the wet season. It tends to rise up the western slope during the mornings and spill over the ridge and flow down the eastern slope, dissipating as the air warms on its descent. The fog on the west side of the range usually dissipates in the afternoon unless cloud keeps temperatures down. Fog is also common in the early mornings in the wet season in the lowest areas at the base of the east side of the Pic de Fon and Oueleba range. A temperature inversion causes fog to form in the lowest parts of the landscape. As temperatures rise and the inversion lifts the fog rises, temporarily causing foggy conditions in Canga East camp. Figure 3.18 indicates that fog at Canga East and Oueleba is more prevalent between the hours of 16:00 and 08:00 than between 08:00 and 16:00. Dewpoint temperatures are usually exceeded between 08:00 and 16:00 hours. While fog adversely affects visibility, fog is also important to plants and vegetation. When water condenses on foliage it reduces the transpiration of water via leaf stomata and the need to take up water via the root system. As yet, attempts to make measurements at the project site of approximate amounts of water that fog can deliver to plants have not been successful. Hail is an occasional form of precipitation at Simandou. Its occurrence indicates temperatures aloft of below zero. Hail stones of up to 10 mm in diameter have been observed at Canga East and at Oueleba camp. Formal records of the occurrence of hail have not been kept. Rainfall is the dominant form of precipitation at the project site. The remaining discussion focuses on rainfall. Rainfall mechanisms The key rainfall generating mechanisms at the project site are: In the dry season localised convection with moisture provided by brief incursions of humid air from the south. The UKMO has suggested that moisture from the forest to the west of the range is a possible source. However, on the basis that the occurrence of fog and rainfall has been observed to occur only during incursions of moist air the forest alone is considered unlikely to provide sufficient moisture. Cloud resulting from convection during the dry season has been observed to occur preferentially over the Simandou range. In the wet season squall lines and easterly waves travelling westwards across country and localised convection cause rainfall over the Simandou range. Rainfall is also caused by forced ascent of moist monsoon air over the ridge from the west and south west when the monsoon air is relatively deep. Further discussion of rainfall mechanisms can be found in the UKMO report in Annex A. Rainfall distribution Figure 3.1 shows the spatial distribution of estimated mean annual rainfall for the period The rainfall record at Canga East began in January 2002 and is the most complete record of rainfall at the project site. Mean annual rainfall at Canga East for the period is 1675 mm. Rainfall records at other stations in the project area have been extended by double mass analysis with Canga East and using the resulting linear regression relationships to predict their rainfall based on that at Canga East.

26 Information specific to the project area 17 Figure 3.1 suggests that there is a zone of high rainfall of mm yr -1 over the northern end of the Pic de Fon range. The zone is oriented north-south and is broadly centred over the ridge. The zone of high rainfall is limited to the north and south by the lower rainfall estimated at Dabatini and at Fokou Centre and Fokou West. A second zone of rainfall over 2000 mm yr -1 is suggested in the south east at Fokou East. This is possibly caused by the hills between Fokou East rain gauge and Foma village. As part of the empirical study of the effect of topography and aspect on rainfall, Figure 3.19 shows rainfall profiles along four transects (see Figure 3.1 for the locations of the transects). The northern transect crosses Oueleba. The central transect links Banko in the west, Dabatini, Canga East and Mafindou to the east of the area shown on the map. The central southern transect crosses the central part of the Pic de Fon ridge. The southern transect crosses the southern part of the project site. On each transect profiles of measured rainfall are presented for three 2-month periods: July-August 2007 (representing the height of the wet season these were particularly wet months in 2007), October-November (representing neither particularly wet nor particularly dry conditions) and December 2007-January 2008 (representing the height of the dry season). While the rainfall profiles shown in Figure 3.19 are snapshots of what happened in particular months, the influence of aspect and topography is clear and the profiles may reflect general relationships. Rainfall over the lowlands is, overall, higher to the west of the range than to the east. Rainfall rises with altitude on both sides of the range. Rainfall gradients are particularly steep and complex at the height of the wet season and in the area of the Pic de Fon (Western Spur, Dabatini and Whisky 1 and 2 rain gauges). Dabatini received much less rainfall in July-August 2007 than the east and west slopes of the range (as represented by Whisky 1 and Whisky 2 rain gauges). The western spur received even less rainfall than Dabatini. Rain gauge WS980 (at 980 m) on the Western Spur, below rain gauge WS1210, received slightly more rainfall than WS1210. This suggests displacement of storm clouds eastwards and westwards from the narrow ridge line by wind currents so that rainfall received by the top of the ridge is less than the slopes. This effect is seen on all (red and orange) profiles under rainy season conditions. During December 2007-January 2008 rainfall amounts were extremely low and topography and aspect exerted little influence on rainfall along any of the (green) profiles. These observations are in line with the mechanisms discussed in the UKMO report in Annex A. Rainfall variability Figure 3.20 shows the monthly and annual rainfall records at Canga East. There is a strong seasonality to the rainfall distribution. On average 93% of the annual rainfall at Canga East falls in the eight month period from 1 March to 31 October. Rainfall is variable from year to year. Rainfall at Canga East in 2006 was 1346 mm and 2030 mm in 2007, representing anomalies of -20% and 21% of the annual mean of 1675 mm. Table 3.7 summarises monthly rainfall statistics and provides daily maximum rainfalls recorded by the long term automatic weather stations at the project site.

27 18 Information specific to the project area Table 3.7 Summary data on rainfall (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Canga East daily rain gauge (Jan Dec 2008) Monthly mean Monthly max Monthly min Daily max n Fokou West automatic weather station (Mar Dec 2008) Monthly mean Monthly max Monthly min Daily max n Dabatini automatic weather station (Dec Dec 2008) Monthly mean Monthly max Monthly min Daily max n Mafindou automatic weather station (Dec Dec 2008) Monthly mean Monthly max Monthly min Daily max n Mandou automatic weather station (Dec Dec 2008) Monthly mean Monthly max Monthly min Daily max n Oueleba automatic weather station (Jul 2007 Dec 2008) Monthly mean Monthly max Monthly min Daily max n n = number of months of record. Diurnal variability Rainfall is variable diurnally at the project site. Figure 3.21 shows the percentage of recorded rainfall occurring in each half hour period of the day for Dabatini at the northern end of the Pic de Fon site and for Fokou Centre rain gauge situated on the crest of the range at the southern end of the Pic de Fon site. At Dabatini in the wet season rainfall is distributed relatively evenly throughout the day. In the dry season there are rainfall peaks between 09:00 and 10:30 hours and between 15:00 and 19:30 hours. At the southern end of the Pic de Fon site rainfall in the wet season is also distributed throughout the day, but more rain falls from 13:00 to 01:30 hours. The diurnal variation is very marked in the dry season with clear peaks in rainfall between 01:00 and 02:30 hours and between 15:00 and 18:00 hours, related to the timing of convection.

28 Information specific to the project area 19 Rainfall intensities Rainfall at the project site can be intense, resulting from convective activity and thunderstorms. Table 3.7 provides maximum daily rainfalls on record ( ) at each of the long term rain gauges in the project area. The highest daily fall on record is 179 mm which has been recorded twice, once at Dabatini on 9 January 2005 and once at Mandou on 8 July With the exception of the 9 January 2005 event at Dabatini, the maximum daily rainfalls listed in Table 3.8 have occurred in July or August, the wettest months of the year. Table 3.8 gives the maximum rainfall intensities on record for storms of 0.5, 1 and 1.5 hours duration. High rainfall intensities occur over both high and low ground. There is some evidence that high intensities only occur for short periods over low ground, whereas they may be maintained for longer over high ground. Table 3.8 Maximum short-term rainfall depths and intensities recorded at the project site, Station Parameter 30 minutes 1 hour 1.5 hours Dabatini Depth (mm) Intensity (mm/hr) Date 2 Aug Mar Mar 2004 Mafindou Depth (mm) Intensity (mm/hr) Date 30 Oct May Sep 2005 Mandou Depth (mm) Intensity (mm/hr) Date 8 Jul Jul Jul 2003 Thunder storms Records of thunderstorms began in May Figure 3.22 shows the seasonal and diurnal variation in the number of thunderstorms recorded at Canga East. Maximum thunderstorm activity occurs between the hours of 16:00 and 08:00, as for rainfall (Figure 3.21). Peak activity during these hours occurs in July with a secondary peak in November. Thunderstorms also occur during the period 08:00 to 16:00 hours. Peak activity during these hours is in June with a secondary peak in September Historical climate change Moving means and linear regression are used here to detect change on a decadal timescale and in the long term respectively. Figures 3.23A and 3.23B show the annual rainfall and temperature records at Beyla, Kerouane, Kissidougou, Macenta and Nzérékoré. In general the records are too short to make a valuable inference on climate change. However, the following observations are made.

29 20 Information specific to the project area The rainfall record at Beyla is in two parts, both too short to fit a long term trend line with confidence. The rainfall record at Kerouane dates from 1956 and, despite missing records, suggests a long term downward trend in rainfall. This is also suggested by the more complete records at Kissidougou and Nzérékoré which show a long term downward trend in rainfall from the 1930s to the present day. The trend is most marked at Kissidougou, but comparable to that at Kerouane. The 10-year moving means applied to the rainfall records indicate that cyclic change takes place on a decadal timescale and that similarities exist between the stations. Periods of higher rainfall at Beyla included the 1930s to late 1940s, and the early- to mid- 1950s. A period of lower rainfall started at the end of the 1950s and continued into the 1960s. There is a break in the record from 1963 until The 1980s appear to have been a period of low rainfall at Beyla. However, since about 1990 rainfall at Beyla seems to have been increasing. These patterns are replicated at Kissidougou whose long term record shows a downward trend from the 1960s ending in the early 1990s since when there has been increasing rainfall. These patterns were also found by Gauthier et al (1998) and Balme et al (2006) whose studies covered a wider area of West Africa (see Annex A, page 12). The first five years of the 21 st century appears to be a period of increasing rainfall. Cycles in rainfall may be expected in future. The annual temperature records at Beyla and Kerouane are too incomplete to indicate trends. However records at Nzerekore and Kissidougou indicate there is a gradual long term upward trend in annual mean, mean maximum and mean minimum temperatures. Other factors being equal, such trends would imply a trend toward higher evaporation Future climate change A review was carried out by the UK Met Office of the published scientific literature concerned with predicting future climate change in West Africa using climate models (Annex E). The relatively few studies that were found do not show a significant change in precipitation in the Guinean region. Where a significant change in precipitation due to climate change is shown by climate models for the Guinean region, it tends to be an increase. A straightforward average across the ensemble of 21 climate models considered by the latest IPCC (Inter-governmental Panel on Climate Change) report results in modest moistening in the Sahel (to the north of Simandou) with little change on the Guinean coast.

30 21 REFERENCES Allen RG, Pereira LS, Raes D, Smith M Crop evapotranspiration. Guidelines for computing crop water requirements. Irrigation and Drainage Paper 56, Food and Agriculture of the United Nations, Rome. Balme M et al Années seches et années humides au Sahel: quo vadimus Hydrological Sciences Journal, 51(2). Barry AB and Sivakumar MVK Agroclimatologie de l Afrique de l Ouest: la Guinée. Rapport pour la Direction Nationale de la Météorologie, Conakry, par l Institut International de Recherche sur les Cultures des Zones Tropicales Semi-Arides (ICRISAT) et le Centre Africain pour les Applications de la Météorologie au Developpement (ACMAD). Gauthier F et al Variabilité du regime pluviometrique de l Afrique de l Ouest non sahelienne entre 1959 et Hydrological Sciences Journal, 43(6). Penman H L Natural evaporation from open water, bare soil and grass. Proc. R. Soc. London, Ser. A

31 22 References THIS PAGE HAS BEEN LEFT BLANK INTENTIONALLY

32 Figure 3.1 Meteorological monitoring network and estimated mean annual rainfall in project area Legend RainGauges Kilometres Hydrometric points W X Automatic weather station (AWS) Automatic rain gauge Senegal ± Mali Guinea-Bissau Manual rain gauge I Highest Elevations J Nionsamoridou Nionsamoridou 1210 Guinea J Villages RainContours_2002_08 13 Sierra Leone Cote d'ivoire Revised river network Road Liberia Contours (5 meter Interval) Index Map Siatouro J Traorella Lancéodougou (abandoned) J J 1551 Traorela 1740 CMT Wataferedou 1425 J 14 Korella J Wataferedou Whisky 5 Oueleba AWS 1838 I X W Pic du Oueleba (1330m) 1723 Whisky 6 Lamadougou J Moribadou J Moribadou Orono J Mandou Mandou J 1683 Kotila J I Western Spur 1210 Banko Canga East Dabatini 2370 Western Spur Banko J W X Mandou AWS Pic de Fon (1656m) 2256 Whisky Whisky Whisky J Tourela Fokou Centre Fokou East W X Fokou West AWS Tourela Foma 1394 J Foma P:\1849_Simandou\Reports\Draft social and environmental baseline report\section 6.9 Hydrology\Figures\Figure 3.1 Meteorological monitoring network and estimated mean annual rainfall in project area Loffa R at Foma Simandou / 1849

33 Figure 3.15 Relative humidity at Dabatini, June 2004-May Mar-2008 Dabatini Automatic Weather Station DAB AWS Daily Mean Relativ e Humidity (%) Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May 2004 Dabatini Automatic Weather Station DAB AWS Monthly Mean Relative Humidity (%) Relative humidity (%) Relative h umidity (%) Rio Tinto Iron Ore Atlantic Ltd P:\1849_Simandou\GIS\Maps\Peter\April01\Figure 3.15 Relative Humidity at Dabatini June 2004 May 2005.mxd Simandou/1849

34 Figure 3.16 Diurnal variation in relative humidity in the wet and dry seasons at Dabatini July 2007 (wet season) 15 January 2008 (dry season) :00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 00:00 Relative humidity (%) P:\1849_Simandou\GIS\Maps\Peter\April01\Figure 3.16 Diurnal Variation in Relative Humidity in the Wet and Dry Seasons at Dabatini.mxd Simandou/1849

35 Figure 3.17 Daily potential evapotranspiration and open water evaporation at Dabatini, Apr Evaporation (mm) Evaporation (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2007 Dabatini Automatic Weather Station DAB AWS Daily Potential Evapotranspiration PET (mm) Dabatini Automatic Weather Station DAB AWS Daily Open Water Evaporation Eo (mm) Rio Tinto Iron Ore Atlantic Ltd P:\1849_Simandou\GIS\Maps\Peter\April01\Figure 3.17 Daily Potential Evapotransporation and open water evaporation at Dabatini 2007.mxd Simandou/1849

36 Figure 3.20 Monthly and annual rainfall at Canga East, Annual Rainfall (mm) Canga East Camp CEC RG Rainfall main series (mm) Monthly Total (mm) Canga East Camp CEC RG Rainfall observed (mm) Annual Total (mm) Second Axis Monthly Rainfall (mm) Rio Tinto Iron Ore Atlantic Ltd Jan-2009 P:\1849_Simandou\GIS\Maps\Peter\April01\Figure 3.20 Monthly and annual rainfall at Canga East mxd Simandou/1849