GIS based Multi Criteria Analysis in Mapping Potential for Irrigated Agriculture. Case study: Machakos County
Agriculture in Kenya is fundamental in economic development, it contributes 35% of the gross domestic product and such remains the backbone of the economy, it’s growth is important for alleviation of poverty and stimulation of economic growth and development. Economic growth and development envisioned in the Kenya Vision 2030 can only be achieved by investing and transforming this sector of the economy which ensures constant food supply and food security for the population. Through all this multiplier effects agriculture is perceived to be an engine of economic growth and development. It’s the main economic activity in rural areas. However this sector has suffered a setback as a result of over reliance to rainfall which is insufficient in most areas. Kenya’s dry land areas, Arid and semi-arid makeup more than 80% of the country (Umar 1997). As a result there has been an imbalance between food demand and supply. Increasing population numbers intensify the pressure on agricultural resources and to meet the nutritional demands of the growing population, an increased food supply is required. It’s on this backdrop that irrigated agriculture should be developed in this country to complement rain fed agriculture especially in arid and semi arid areas with rivers and other water bodies. Geographic Information Systems (GIS) based Multi criteria analysis can be employed to map areas with potential for irrigation. Focusing on Machakos County as the case study, this project explored how GIS can be used to identify areas with potential for irrigated agriculture thus expanding area under crop production in this County. Multi criteria analysis is concerned with the allocation of land to suit a specific objective on the basis of a variety of attributes that the selected areas should possess (JR Eastman,1999). The Project focused on different variables including soil fertility (soil texture, depth and Ph), drainage (perennial rivers), land use land cover, topography and road infrastructure. GIS tools; the model builder, was used to analyze the data sets and result were presented using Suitability maps, tables and graphs. SRTM 30m was used to extract slope data and Google earth images used for validation. vi Results from this work showed that 2602Km² accounting for 41.9% of the total area was highly suitable for agriculture. 3355Km² accounting for 54.03% was moderately suitable for irrigation, 78km² accounting for 1.26% was found to be marginally suitable for irrigation whereas 175Km² accounting for 2.81% was found to be unsuitable for irrigated agriculture. The results also illustrate how GIS as a tool can be used in exploration of water resources in a scientific approach hence making decision making easier and accurate. The findings from the study will help in developing policies and strategies to address the perennial food shortage in Machakos County by among others the County Government of Machakos, Ministry of Agriculture and Non – Governmental Organisations.