JOURNAL OF THE DRYLANDS 3(2): 214-219, 2010 214-219, 2010 Land Suitability Assessment for Different Irrigation Methods in Korir Watershed, Northern Ethiopia Kassa Teka1, 2*, Van Rompaey, A.2 and Poesen, J.2 Kassa Teka, Van Rompaey, A. and Poesen, J. 2010. Land Suitability Assessment for Different Irrigation Methods in Korir Watershed, Northern Ethiopia. Journal of the Drylands 3(2): 214-219 In much of Korir watershed the surface irrigation system is a common practice applied for maize, vegetables and fruit trees to meet water needs. There are very few instances of drip irrigation on small farms in the area. The aim of this research was to evaluate and compare land suitability for surface and drip irrigation methods based on the parametric evaluation systems. Suitability maps were generated for surface and drip irrigation methods by means of Remote Sensing Technique and Geographic Information System (GIS). Study results showed that for surface irrigation, there is no area classified as S1. Only 28.77% and 91.54% of the study area is with in the suitable range for surface and drip irrigation respectively. The mean capability index for surface irrigation was 45.82 (marginally suitable) while for drip irrigation 60.6 (moderately suitable). The results indicate that by applying drip irrigation instead of surface irrigation methods, 62.77% can be improved from N1 to S3 and 6.19% and 22.58% from S3 and S2 respectively to S1. The comparison of the different types of irrigation revealed that the drip irrigation was more effective and efficient than the surface irrigation methods. Key words: Surface, drip, suitability, watershed, irrigation, Korir 1Department of Land Resources Management and Environmental Protection, Mekelle University, P.O.Box 231, Mekelle University 2Physical and Regional Geography Research Group, K.U.Leuven, Celestijnenlaan 200E, BE-3001, Leuven, Belgium *Corresponding author: kassateka@yahoo.com, Tel: +251-0914726677 Received August 10, 2010, Accepted November 25, 2010. INTRODUCTION The environmental situation in Africa, with deforestation and soil degradation etc., is a very worrying (Foty, 1993) and irrigated area per capita is declining and irrigated lands now produce 40% of the food supply (Hargreaves and Mekley, 1998). Consequently, the available water resources may not be able to meet various demands in near future that will inevitably result in the irrigation of additional lands in order to achieve a sustainable global food security. To develop sustainable use; one has to know the limitations and potentials of the land. The best uses for land depend on soil characteristics and their response to the use such as texture, rooting depth, stoniness, rockiness, organic matter content, nutrient status, structures, drainage conditions, slope, etc. Sys et al. (1991) suggested a parametric evaluation system for irrigation methods which was primarily based upon physical and chemical soil properties. These factors influence the land suitability in an irrigation practice including soil properties and topography. Hired et al. (1996); Bond (2002) and Briza et al. (2001) applied a parametric system (Sys et al., 1991) to evaluate land suitability for both surface1 and drip2 irrigation 1 With drip or trickle irrigation the water is applied into the soil through a small sized opening directly on the soil surface or buried in the soil. By applying water at a very slow rate, drip irrigation is capable of delivering water to the roots of individual plants as often as desired and at a relatively low cost (Sijali, 2001). in Morocco, while no highly suitable areas were found in the studied area. The largest part of the agricultural areas was classified as marginally suitable. However, a large difference between applying the two different evaluations was obtained (Bazzani and Incerti, 2002). The area not suitable for surface irrigation was 29.22% of total surface and 9% with the drip irrigation while the suitable area was 19% versus 70%. Land suitability evaluation for surface and drip irrigation conducted (Bienvenue et al. 2003) in Senegal, using the parametric evaluation system showed no area classified as highly suitable (S1) for surface irrigation. Only 20.24% of the study area proved suitable (S2 7.73%) or slightly suitable (S3 12.51%). Most of the study area (57.66%) was classified as unsuitable (N2). For drip (localized) irrigation, a good portion (45.25%) of the area was suitable (S2) while 25.03% was classified as highly suitable (S1) and only a small portion was currently not suitable (N1, 5.83%) or unsuitable (N2, 5.83%). Mbodj et al. (2004) performed a land suitability evaluation for two types of irrigation, (surface irrigation and drip irrigation) in Tunisia using the suggested parametric evaluation. According to the results, the drip irrigation suitability gave more irrigable areas compared to 2 The surface method of irrigation involves applying water over the soil surface. The water is conveyed over the soil surface and infiltrates into the soil at a rate determined by the infiltration capacity of the soil (Sijali, 2001). Copyright Journal of the Drylands 2010 ISSN 1817-3322 34 4 3 4 Very low Low Medium High Very high EC (dS/m) 0 -2 2 -4 4 -8 8 -16 > 16 CEC (cmol(+)/kg 0 -3 3 -7 7 -15 15 -30 >30 Ntot (g/100g) 0 0.1 0.1 0.2 0.2 0.3 0.3 0.4 > 0.4 Ctot (g/100g) 0 0.6 0.6 1.2 1.2 3.0 3 8.7 > 8.7 pH (H2O) 5 -6 6 -7 7 -8 8 -9 9 -10 Moderately acid Slightly acid Slightly alkaline Moderately alkaline Strongly alkaline CaCO3 (g/100g) 0 0.5 0.5 2.0 2.0 5.0 5.0 -15 > 15 Pav (g/100g) 0 0.4 0.4 1.3 1.3 2.6 2.6 5.3 > 5.3 Capability Index Class Definition Symbol >80 I Highly suitable S1 60-80 II Moderately suitable S2 45-60 III Marginally suitable S3 30-45 IV Currently not suitable N1 7 cm/h) such as sandy soils, or soils with final infiltration rates that are too low (