Index and Factors on Drought Resistance of Irrigation Districts against Abnormal Dry Weather

Measures for water shortage in Hokuriku region, 1994

Abstract

Each irrigation district determines the time to enforce drought measures based on a comprehensive analysis of relevant information on river discharge, weather forecasts, irrigation ability etc. This action is similar to that of a living creature protecting its body from lack of water. Based on this idea, this paper clarifies the efficiency index of drought resistance of irrigation districts and regions, which is the difference between cumulative rainfall amount from start of irrigation to commencement of drought measures and the average value for the same period in the past 30 years. In addition, an inverse relation was found between the difference of the cumulative rainfall amount and the utility ratio of water resources in the respective regions.
As for factors influencing the drought in each irrigation district, the area rate of drought occurrence (damaged area/total area) tends to be high in the order of 1) large-area districts where rotational irrigation is conducted, 2) districts utilizing small ponds as major water sources, and 3) small-area districts. The cost of drought measures per unit area tends to be low in the order of 1) large-area districts, 2) districts located downstream large rivers, and 3) districts with small-area to which supplementary water was supplied from other water sources.