Performance evaluation of the Tha Ngon Irrigation Scheme, Xaythany District, Vientiane Capital, Lao People's Democratic Republic

The study focused on the performance evaluation of the Tha Ngon Irrigation Scheme in the Xaythany District, Vientiane Capital, Lao People's Democratic Republic (Lao PDR). In an agricultural country like the Lao PDR, one of the measures to address the problem of food security is by increasing intensity and yield. Cropping intensity and yield can be increased by providing sufficient amount of water all year round. Through performance evaluation, the adequacy to supply water, the timeliness of the water delivery and the equitable distribution or allocation of water throughout the system can be determined. The study evaluated the water use and agricultural productivity performance of the Tha Ngon Irrigation Scheme using the following indicators: relative water supply (RWS), irrigated area performance (F), gross irrigation water quota (M), yield per unit area (Y), and yield per unit quantity of irrigation water (Yw). Based on the results, the high value of the relative water supply (4.35), and the high value of the irrigated area performance (84.6%), and the gross irrigation water quota (7,852 m3/ha) indicated an overabundance of water in the Tha Ngon Irrigation Scheme. Thus, the field evaluation showed that the delivery of water was inefficient likely due to the damaged irrigation structures and the presence of vegetation and debris in the canal. The overabundance of water was confirmed by the obtained yield per unit quantity of irrigation water of 0.148 kg/m sup 3 of water on the average. This over abundance of water resulted to a relatively high yield level of 4,475 kg/ha. As a whole, the results showed that water use performance of the Tha Ngon Irrigation Scheme should be improved in all its other performance indicators. In particular, rehabilitation of irrigation structures and regular maintenance of canals are recommended in order to improve performance of the irrigation system.