Promoting Usage of Effective Rainfall in Pond Irrigation System

Abstract

The pond irrigation system, which is an example of the great wisdom of our ancestors in the early twentieth century, increases the effective rainfall by using geographic features to overcome hydrologic disadvantages. The concept of the pond irrigation system is to reserve excess runoff in farm ponds as if in small reservoirs and then to supply water to farmland during drought periods. The purpose of this study is to promote the original function of the pond irrigation system in Tao-Yuan Area. The irrigation system model shows how agriculture water demand in a region can be satisfied by adjusting system dynamics such as canals, river weirs, and farm ponds. Two methods are (1) deep-ponding irrigation and (2) adjusting the backup storage ratio of farm ponds between up and down stream. The analytical results show that deep-ponding irrigation can use effective rainfall to reduce agricultural water demand from Shih-Men Reservoir and increase the efficiency of water used for farming. Furthermore, during drought periods and/or periods of inadequate reservoir water supply, the downstream region adopts higher ratio in backup storage than upstream, can reduce excessive reserving water in upper ponds and increase storage capacity in lower ponds to store more return flow.