Water management strategies for improving irrigation system performance of Mae Taeng Irrigation System in Chiang Mai Province, Thailand

This study was conducted to determine the performance of Mae Taeng Irrigation System from January, 2003 to May, 2003. An attempt was made to assess the infrastructures in the MTIS in quantitative terms by assigning a range of values to the qualitative description on the functional status of the individual structure. The infrastructures were grouped into three components, namely; a) water control structures, b) conveyance and drainage channels, and c) road network. However, because of the enormous number of structures, the qualitative assessment based on the overall ocular observation in the field was employed rather than the quantitative approach in general, the infrastructure in the MTIS could be considered satisfactory to very satisfactory, since practically all are functional except for minor repairs and improvements. A modified conceptual model for determining the irrigation system performance index (ISPI) of the MTIS was introduced. The model used by previous researchers was composed of three indicators to measure the ISPI, namely, equity, productivity, and water use efficiency. The modified model includes the farmers' satisfaction rating in addition to the three indicators in the original model. Following the modified conceptual model, each of the four indicators was evaluated for each of the four sections of the MTIS using scoring schemes for multiple crop condition. The result of the evaluation showed that the weighted scores of equity, productivity, water use efficiency, and farmers' satisfaction rating were 11.97, 16.53, 15.00, and 19.50, respectively for a total of 63.00 or an ISPI of 0.63. Applying the model without the satisfaction rating indicator, the ISPI comes up to only 0.58 which is a little lower than using the modified model. Therefore, the farmers' satisfaction rating affects the ISPI either on the negative or positive way. In order to interpret the result of the evaluation in its proper perspective and for purposes of comparison with other irrigation systems, a new scoring scheme was introduced indicating the range of values of the ISPI corresponding to their qualitative description as poor, satisfactory, or very satisfactory. The ISPI of the MTIS as evaluated could be considered satisfactory. Based on the results of this study, a number of operational management strategies were identified including early cropping in December in order to take advantage of the abundance of water available, installation of flow measuring devices for monitoring and control, installation of pumping stations along the Ping River, and construction of a reservoir upstream for water supply augmentation for irrigation, domestic, recreational and industrial needs of Chiang Mai Province.