HYDROPEDOLOGY AND WATER RESOURCES MANAGEMENT: CASE STUDY OF AL-KHOUD RECHARGE DAM- OMAN

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1 HYDROPEDOLOGY AND WATER RESOURCES MANAGEMENT: CASE STUDY OF AL-KHOUD RECHARGE DAM- OMAN Dr. Ali Al-Maktoumi Sultan Qaboos University, Oman Gulf Water Conference 11 th October 2014 Co-authors: Al-Saqri, S; Faber, Z.; Al-Ismaily, S.; Kacimov, A. ; Al- Busaidi, H;

2 Introduction Recharge dams is one of the effective means for augmenting water resources in arid climate (e.g., Arabian peninsula) Recharge dams- siltation is a common problem: Clogging /reduction in retention capacity problem Potential flooding hazard Fine soil particles are brought to the recharge basin due to over-spilling

3 Main Objectives Investigate the impacts of anthropogenic activities (construction of Al-Khoud dam) on the physiochemical properties of the subsurface porous medium in a dry region of Oman. To assess the consequent impacts on hydraulic properties which are important for the recharge of the underlying aquifers.

4 Oman The study Area

5 Methodology Residential area Abstraction wells Residential area Sampling (33-pedons)

$Sand fractionation EC, ph$ Calcimeter XRD SEM

6 Methodology (cont d) Physical Chemical & mineralogical Hydrological Soil Texture, Hydrometer Sand fractionation EC, ph and Cations (ICP) Calcimeter XRD SEM Infiltration tests (Tension infiltrometer) 7 selective tests

7 Scatters of different vegetative patterns in the lake area

8 Soil Pedons of the Al-Khod Dam bed, 23 years after dam construction

9 Incipient and mature pedogenic features of the study area.

10 Accumulated sediment analysis Suspended load will be quantified as Total Suspended Solids (mg/l) Bed load as the thickness of FSS (fine soil sediments silt + clay + very fine sand) deposition on soil surface A torrential rain event occurred in Muscat- Oman during the period 28 th April 3 rd May, 2013 which was an opportunity for this study

11 Suspended Load

12 Turbidity of the Wadi water High-velocity flow through the sluice gates and over the dam crest Sediments are reagitated and brought back into suspension flowing into the stilling basin and recharge basin

volume was reduced since the dam construction Total volume that the

14 Bed Load Transect 1 was used to estimate the change in Al-Khoud dam water retention capacity It was estimated that > 30% of the storage volume was reduced since the dam construction Total volume that the dam can store is around 8 million m 3 instead of 11.7 million m 3

15 Wadi Hydrograph Source of Data : Ministry of Regional Municipalities and Water Resources

16 Translocation of FSS to subsurface soils Depends on soil texture, structure and pore size Physical clogging was observed and explored Likely, FSS vertically moved downward with the seeping water until particles are retained within pores

17 Mineralogical analysis XRD technique was used to quantify crystalline compounds in soil SEM was used in geochemical and mineral studies for the purpose of having closer inspection on the mineral surfaces, topography, morphology and composition Total 8 samples

18 Soil Density and Packing (Microscopic Scale) Higher coated matrix (Inside dam) Less coated matrix (Outside dam) Denser soil fabric with more packing/coating between the soil grains of soils inside the dam area.

19 Pedon E Ca E Mg Geogenic discontinuity Flicks of calcic materials (Field Observations) Ca Mg Petrographic Techniques

20 Vertical translocation of fine soil particles into the subsurface.

21 time (hour) x (cm)

22 M is accumulated mass of translocated particles in drained samples δ is mass of translocated particles in drained samples

23 Infiltration experiments Ks values of the selected pedons of the study area. Pedon Latitude Longitude Ks (m/day) Ks (cm/hr) AA AC AG I K O-surface O- (80 cm) R

24 Conclusions Reduction in storage capacity of recharge dams along with the obvious reduction in the infiltration rate of the reservoir bed, would results in more frequent over spilling of unclear water to recharge basin. Evolution of the physicalochemical characteristics of the subsurface soils in the vicinity of the recharge dams, affects its hydraulic properties that ultimately will deteriorate the recharge process. Presence of calcic materials coating at the bottom of rocks was observed at the pedological discontinuity with the soil horizons. This particle coating would grow with time resulting in chemical clogging The saturated hydraulic conductivity reduced by nearley 10 times when clogging take place (from both, field and column experiments)

25 Thank you

C) D) 3. Which graph best represents the relationship between soil particle size and the rate at which water infiltrates permeable soil?

C) D) 3. Which graph best represents the relationship between soil particle size and the rate at which water infiltrates permeable soil? 1. Which earth material covering the surface of a landfill would permit the least amount of rainwater to infiltrate the surface? A) silt B) clay C) sand D) pebbles 2. Which graph best represents the relationship