Irrigation Efficiency of the Greater Chao Phraya and the Greater Mae Klong Irrigation Projects

Abstract

The irrigation efficiency of each block of the Greater Chao Phraya Irrigation Project(GCPP) and the Greater Mae Klong Irrigation Project(GMKP) were calculated on both wet and dry season during 1995-1998. GCPP was divided into 18 blocks. Each block in GCPP covered the area of one or more irrigation subproject according to the hydraulic boundary of the irrigation area such that the inflow and the outflow of the block could be measured. GMKP was divided into 10 blocks. Each block in GMKP was the same as the irrigation subproject. The Ei of GCPP varied between 14.6-55.4% with the average value of 39.4%. The Ei of GMKP varied between 24.5-51.0% with the average value of 43.2%. In general, the Ei of GMKP was about 4% higher than that of GCPP. Both GCPP and GMKP used the continuous water delivery with the upstream control practices. The Ei on both GCPP and GMKP varied considerably. Borommthart project on the upper right bank of GCPP had the highest Ei of 63.7% while Pakhai project had the lowest Ei of 13.3%. For GMKP, Song Phi Nong project on the upper left bank had the highest Ei of 66.8% while Thamaka project on the right bank had the lowest Ei of 19.2%. The wet season Ei on both GCPP and GMKP had a linear relationship with the annual rainfall. The dry season Ei was linearly related to the water available at the beginning of the dry season and the irrigated area. Besides, the irrigated area was highly correlated to the available water.