BY WASIKE L ARNOLD F19/1669/2009 APPLICATION OF GEOSPATIAL TECHNOLOGIES IN THE SELECTION OF A SUITABLE DAM SITE ON THE LOWER EWASO NYIRO RIVER

INTRODUCTION Narok and Kajiado north counties describe areas that have been grossly under developed due to the predominant arid and semi- arid conditions. The Ewaso Nyiro basin, being in this area presents a possible solution to this problem by providing a very essential resource, water. Damming has been identified as a way of ensuring constant supply of water over the different seasons The focus of this project is to identify an area on the river within the river valley, using GIS and mapping tools that will be most suitable for the location of the dam

PROBLEM STATEMENT A dam is needed in the area in order to ensure constant water supply which forms part of the initiatives for economic development in the area. The main problem is to establish a suitable location that a dam could be constructed depending on a number of factors that have been conventionally identified This will be solved by considering the affecting factors as criteria and carrying out multi-criteria suitability analysis using GIS tools on order to arrive at a result showing the proposed dam site location

OBJECTIVES Main Objective Identify a suitable dam site on the lower Ewaso Nyiro River with the aid of Geospatial technologies. Specific objectives To identify criteria for selecting a suitable dam site and establish respective weights To produce a suitability map for each criterion To carry out multi criteria analysis resulting in the production of the final dam site suitability map To review the results and draw appropriate conclusions and recommendations

METHODOLOGY STAGE ONE INTRODUCTORY BACKGROUND REVIEW OF RELATED LITERATURE CONCEPTUAL ANALYSIS STAGE TWO DATA TYPES AND SOURCES DATA TYPES - Cadastral Maps -Aerial imagery -Geology Maps DATA ANALYSIS -Data Compilation -Spatial analysis DATA PRESENTATION -Maps STAGE THREE RESULTS FINDINGS AND PRESENTATION ANALYTICAL PRESENTATION Model CONCLUSION - Conclusion -Recommendations

CRITERIA ADOPTED CRITERIONPARAMETERS Human activity 1 km from zones and 500 m from points. Fault lines500 m from fault lines RiverWithin a 250 meter corridor of the river GeologyAreas with a stability value of ≥ 5 ElevationAreas with a slope of ≥ 50%

WEIGHTING CriterionWeight Proximity to the river33% Stable rock foundation27% Topography20% Fault lines13% Human activity7% Weighting by rank order formula

AREA OF STUDY Area west of Lake Magadi Covers potions of Narok and Kajiado north counties Area within the Ewaso Nyiro basin To the north of Shompole conservancy

INPUT DATA SETS

Geology Map Levels or rock stability

DEM

Human activities, population points suitability map

Human activities, population zones suitability map

Fault lines suitability map

River suitability map

Slope suitability map

Geology suitability map

Overlaid suitability map for dam location

EXTRACTED SUITABLE AREAS

FINAL DAM LOCATION SUITABILITY MAP

DISCUSSION OF RESULTS A clear zone in which the dam can be constructed was identified. This zone fulfils all the parameters preset in the multi-criteria analysis Levels of accuracy in the raster overlay are dependent on the resolution of the largest data set. For more accurate results, commercial data at a higher resolution can be acquired The results give a zone rather than a point where the dam could be located

CONCLUSION Two zones exist along the river which present the most suitable locations for the dam. All the objectives to the study were achieved RECOMMENDATION An actual simulation of the dam should be done to determine reservoir size and siting within the zones and the hydraulic head; factors which will narrow down the location of the dam within the identified zones

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