Impact of land use on water resources: integrating HSPF and a raster-vector GIS

Transcription

1 HydroGIS 96: Application of Geographic Information Systems in Hydrology and Water Resources Management (Proceedings of the Vienna Conference, April 1996). IAHS Publ. no. 235, Impact of land use on water resources: integrating HSPF and a raster-vector GIS CARLOS TAVARES RIBEIRO Technical University of Lisbon, Civil Engineering Department, Av. Rovisco Pais, 1096 Lisbon Codex, Portugal Abstract The integration of simulation models and GIS technology can be an approach to finding right and well-justified decisions concerning land use and natural resources, and for environmental care. It can also be an interface for the relation municipalities vs citizens with the character of educational practice about land planning and survey. This paper describes the development of IURB-HID, an integrated model using HSPF (Hydrological Simulation Program - FORTRAN) from the US EPA and a raster-vector GIS for PC platform, for the analysis of urbanization and land use impacts on water resources at basin scale. The model and its integration with GIS and its operation procedures are described in detail. The application of IURB-HID to the Ôbidos lagoon basin is also presented and illustrated, as well as the manner in which its results can be used in the decision concerning land use, in relation to its impact on water resources. INTRODUCTION The integration of simulation models and GIS technology can be an approach to the solution for the right and well-justified decisions concerning the land use and natural resources, and for environmental care. Several methodologies and models have been proposed since the early nineties, namely within the scope of the International Hydrological Programme set up by UNESCO, and specially by its subprogramme M-2-3: "The Use of Geographic Information Systems in Hydrological and Water Resources Studies". The methodologies can be described as follows (Maidment, 1991): Determination of hydrological parameters. In this process, the functions of the GIS are used for efficient selection of the parameters required for the functioning and operation of existing hydrological models (Sasowsky & Gardner, 1992). Combinations with hydrological models and GIS. In this process, the GISs are used in the selection of parameters from sets of elementary data. The results of space analysis are presented by making use of GIS functions. Most of the research as regards the integration of hydrological models and GIS now falls within this area (Brilly et al., 1993), like the IURB-HID presented here. Development of GIS based hydrological models. In this process, the hydrological model is an integral part of the GIS, and its construction makes use of the GIS programming language. This methodology is still the least developed.

2 350 Carlos Tavares Ribeiro Within the scope of methodologies for integrating water resources management systems and GIS, two basic situations must be considered: vectorial GIS are adequate for the integration process of overall hydrological models; raster GIS are necessary regarding spatially distributed hydrological models. The modelling of hydrological systems has presented difficulties in the synthesis and combination of data. On one hand, when the number of observation and collecting points is limited. On the other hand when the collection of data does not provide suitable quality and resolution for fully distributed models. The large spatial resolution on which these models operate and the quantity of parameters required, that are, in general, hard to measure in situ and have limited their use (Bathurst, 1993). Partially owing to this kind of difficulty, the semi-distributed model method is an attractive and functional means for hydrological modelling. So, whether GISs are only a complement for hydrological modelling, or whether in fact they will be the platform on which the development of the models takes place, will only depend on overcoming human and technology difficulties to interconnect both (Stuart & Stocks, 1993). In our opinion, these difficulties arise from the initial incapacity of GISs to include data structures of the models and in a lack of flexibility as regards the re-creation of the GIS through an open architecture with possibilities of programming and reconfiguration. In the present application, the consideration of a raster-vector GIS fits in well enough with the spatially distributed data. On the other hand it is also suitable for data that must be processed according to vector capabilities. DATA INSIDE AN INTEGRATED HYDROLOGICAL AND GIS MODEL The vast amount of spatial information needed for hydrological models can be obtained and stored in GIS making it available for the model, constituting a unified system (Kienzle, 1993). The integration of hydrological models and GIS thus consists of establishing processes whereby they communicate with one another, and it has been developed as follows: preparation of the spatial characteristics such as land use, types of soil, etc., by means of GIS; assignment of the hydrological variables (variations) in interception, depth of roots, rate of applying fertilizers, characteristics of the soil as regards retention of water; semi-automatic assignment of these variables to the hydrological model; operation of the model; assignment of the results to the cartographic database of the GIS and options for associated charts. Therefore, the integration of systems seems to consist fundamentally in connecting the components described. THE IURB-HID MODEL The IURB-HID model, has been developed and implemented as an integration of the HSPF of the US EPA (Barnwell & Johnson, 1983) and the raster-vector GIS-PAMAP from EPS, Inc. It makes the construction of various input modules of the HSPF possible

3 Impact of land use on water resources: integrating HSPF and a raster-vector GIS 351 by resorting to GIS operations, and has considerable capacity in the production of thematic cartography. This provides a great and unequivocal capacity for decisions in the field of land use planning and management of natural resources, by the responsible institutions. The simulation of different uses of land, through a cartographic interface once in a GIS environment (Fig. 1), shows changes in the hydrological conditions of a drainage basin through thematic mapping production. At the same time an educational process for bringing awareness from regional and local institutions to the population is held, once the presentation process about land use becomes easier. GIS for the implementation and updating j the databases of the watershed! Hydrological behaviour - discharges, top withs and! i depths for each land use distribution be simulated Use of soil map Topography Segmentation Hydrological Simulation Model Time series for Precipitation, évapotranspiration i Parameters for the initial conditions Alphanumeric DataBase = WW M IIIIIIIII IHIitlll lilllllll LIAA f pnh 'U.ftv IIIIIIIII Ellllllll lilllllll Recommended Uses of Soi! Fig. 1 Conceptual description of IURB-HID.

4 352 Carlos Tavares Ribeiro Components of IURB-HID IURB-HID involves HSPF, PAMAP in its both vector and raster capabilities, editors specifically configured for the preparation and edition of alphanumeric information and interfaces HSPF-PAMAP for the linkage through conversion and transference of data. For some pre- and post-processing procedures, an MS-Windows interface has also been developed. Integration of HSPF and PAMAP Integration of HSPF and PAMAP comes within the scope of the methodology designed as a combination of hydrological models and GIS, for establishing parameters from sets of elementary data, through GIS operations. IURB-HID consists generically of the preparation and analysis of data, both as sequences of input (Fig. 2) in their alphanumeric and cartographic components. Directly or as results of GIS operations, data may in turn and in some cases give rise to HSPF operations. Obtaining outputs, in general alphanumeric, is also the object of processing by resorting to IURB-HID, especially as regards graphic and/or cartographic representation. It is thus a simulation process based on a hydrological model. It involves calibration and verification procedures, for which the use of GIS operations also acquires considerable importance and innovation. The operating procedures of IURB-HID using GIS operations, are presented in detail in Fig. 3 (Ribeiro, 1994). It involves the processing of alphanumeric information (time series indexes relating to precipitation, évapotranspiration, air temperature, solar radiation) and input parameters concerning the basin characteristics (geology, hydrogeology), main land uses and cartographic information. Although IURB-HID, as a tool for the analysis of the impact of urbanization and types of agricultural land use in water resources, does not constitute a spatially distributed model, it takes the raster capabilities of the GIS considered. An included DTM, works as a semi-automatic process in the definition of homogeneous areas (in the model these areas are called Pervious Land Segments, PLS), in the way required by HSPF (Fig. 4), concerning topography, air temperature variations and precipitation contours and classes of land use. ghajbifibgramii». (" * :.*"" *".!. i -- i«.i»>"^*i*,~"j,., ijijpfâiiiisiîiiipi Fig. 2 Structure of the integration of HSPF and GIS.

5 Impact of land use on water resources: integrating HSPF and a raster-vector GIS 353 Q X Dû en

6 354 Carlos Tavares Ribeiro o o f S O O O O O O O O O 2 d Q o o o o o o o c - o o o d o o d d d Q LU o ' o - o o g o o o o o o o, " o o q o o o o o o o c 0 o o o d o o d d d d 00 H Q

7 Impact of land use on water resources: integrating HSPF and a raster-vector GIS 355 The GIS databases produced by the presented operations, under the GIS vector mode, are now converted for the HSPF format through convenient FORTRAN program interfaces. This allows the construction of the input data blocks for the various modules of HSPF specially the NETWORK block relating to the PERLND and IMPLND modules. The FTABLES block referring to the RCHRES module of the HSPF, that consists of sets of parameters of the hydrogeometric properties of cross-sections of the reaches, are also achieved through suitable functions of PAMAP. Fig. 5 Result of one application of IURB-HID for indicated classes of land use.

8 356 Carlos Tavares Ribeiro APPLICATION OF IURB-HID TO THE BASIN OF ÔBIDOS LAGOON The basin of the Ôbidos lagoon located in midwest Portugal is a basin of 500 km 2 draining directly into the Atlantic Ocean. The basin ranges from 0 to 600 a.m.s.l., the air temperature ranges from an average of 20 C to 25 C and the precipitation ranges from 600 to 1000 mm. The application of the IURB-HID is intended to simulate the discharges in streams for land use planning. The input sequence for calibrating the model corresponds to the real areas of agricultural land use and urban areas: PERLND and IMPLND modules of HSPF were considered. Time series of meteorological parameters (precipitation, évapotranspiration and air temperature) has been considered in a daily time step for 5 years. The discharges and depths calculated by the model have been checked against five years of real corresponding records Once the model has been calibrated, the analysis of the impact of urbanization and land use on the water resources for a given land use can now be done. The results are presented in a tabular, chart and mapping formats. The mapping format is an output where streams get colour variations, corresponding to classes of values of discharges. The following features can be superimposed on any map: slopes, orientations, administrative division or land use (Fig. 5). The colours in streams may also be used as warnings for planners of the acceptable limits for discharges in the streams. The analysis process may follow by simulating various land use situations and the inclusion or not of urban areas. Similar maps can be produced for the top width and depth of the streams. Acknowledgements PAMAP is the registered trade mark of Environmental Planning Systems, Inc. MS-Windows is the registered trade mark of Microsoft Corporation. REFERENCES Barnwell, T. & Johnson, R. (1983) HSPF: A comprehensive package for simulation of watershed hydrology and water quality. In: Nonpoint Pollution Control: Tools and Techniques for the Future. Interstate Commission on the Potomac River Basin, Rockville, Maryland. Bathurst.J. C. (1993) Physically based distributedmodelling of an upland catchment using Système Hydrologique Européen. J. Hydrol. 87, Brilly,M.,Smith, M. &Vidmar, A. (1993) Spatially oriented surface water hydrological modelling and GIS. In: Application of Geographic Information Systems in Hydrology and Water Resources Management (ed. by K. Kovar & H. P. Nachtnebel) (Proc. Int. Conf. HydroGIS'93, Vienna, April 1993), IAHS Publ. no Kienzle, S. (1993) Application of a GIS for simulating hydrological responses in developing regions. In: Application of Geographic Information Systems in Hydrology and Water Resources Management (ed. by K. Kovar & H. P. Nachtnebel) (Proc. Int. Conf. HydroGIS'93, Vienna, April 1993), IAHS Publ. no Maidment, D. (1991) GIS and hydrological modelling. In: First Int. Symposium/Workshop on GIS and Environmental Modelling (ed. by M. F. Goodchild, B. O. Parks & L. T. Steyaert) (Boulder, Colorado, September 1991). Oxford University Press, New York. Ribeiro, C. (1994) Urbanisation and soil use impacts in water resources. PhD Thesis, Technical University of Lisbon, Lisbon, Portugal. Sasowsky, K. & Gardner, T. (1992) Watershed configuration and geographic information system parameterization for spur model hydrologie simulations. Wat. Resour. Bull. 27(1), Stuart, N. & Stocks, C. (1993) Hydrological modelling within GIS: an integrated approach. In: Application of Geographic Information Systems in Hydrology and Water Resources Management {sa. by K. Kovar&H. P. Nachtnebel) (Proc. Int. Conf. HydroGIS'93, Vienna, April 1993), IAHS Publ. no. 211.