本研究選取桃園大圳二支線為研究區域，二支線之灌溉水源取自於石門水庫與埔心溪及南崁溪，而桃園地區內的埤塘灌溉系統為特有農業灌溉方式，不僅可以提升降雨量之使用率更能調蓄輔助農業灌 溉用水。因此本研究利用系統動力模式模擬農業灌溉系統，考慮降雨提供之雨量及有限灌溉水源，以2008 年灌區資料進行灌溉用水模 擬。經由改變引灌水量操作方式及河水堰取水量，探討引灌水使用量以及埤塘灌溉系統之調蓄效益。針對埤塘灌溉系統對於農業灌溉之重要性，考慮埤塘灌溉系統於引灌方式上三種不同之操作：正常灌溉、關閉河水堰取水及關閉埤塘灌溉系統進行模擬，發現關閉埤塘灌溉系統對於作物之生長情況最為不利，結果顯示出集中降雨型態的二期作，在無埤塘灌溉系統之情況下有缺水現象產生，由此證實埤塘灌溉系統在極端降雨型態下，埤塘灌溉系統於農業灌溉上所扮演之重要角色。台灣早期的用水量分別為農業用水、民生用水及工業用水，當中以農業用水量為最大宗取水量(70 ~75%)，然而近年來由工業用水與民生用水之用水比例提高，造成農業用水之比例逐漸下降。當面臨缺水時，用水順序以工業用水及民生用水優先，導致農業用水經常面臨分配不均的窘境，此時農田的耕作型態就會由耕種變成休耕。因此本研究將流出灌區下游之逕流量當作新興水資源再次循環利用且不考慮有任何運輸損失，假設迴歸水可回抽至灌溉源頭作為引灌水量利用，發現模擬結果得到一、二期作在使用新興水資源做為灌溉水源後，分別能夠減少原來一、二期作灌溉水量的50.7% 及86.2%。 This research investigated into the influence of irrigation water requirement with the change of irrigation operation including channel supply and wire supply. Its use of irrigation water on the lead and the pond irrigation system has the effect of regulation and storage efficiency benefits. Tao-Yuan Channel #2 Feeder is selected as the study area. The irrigation resource included Shih-men reservoir, Nankan stream and Puxin stream. The agriculture irrigation system model was established by adapting Vensim model and the irrigation water supply data in 2008 was applied. The different simulations of irrigation management are used to estimate the significance of pond irrigation system for agriculture irrigation. The simulation was divided into three cases: (1) normal state,(2) closing of the water intake weir and, (3) closing of the water intake pond. The result shows that closing pond irrigation system adversely affected on growing of the crops. And the water shortage occurred with the centralization rainfall pattern in second crop given the condition of ponds. Therefore, the pond irrigation system is playing an important role in agricultural irrigation under extreme rainfall patterns. The early stage of Taiwan’s water demand included agricultural water, domestic and industrial water. Agriculture water consumption has the largest quantity of water demand (70 ~ 75%), but in recent years, the increasing domestic and industrial water occurred to decrease agricultural water ratio gradually. When facing with the water shortage, domestic and industrial water have high priority induced lack of agricultural water and fields will change cultural type from work to fallow. In this study, the runoff that flowed out from the downstream irrigation section can be reused as new recycling water without transporting loss. Assuming the return flow can be pumped up to upstream irrigation section and be used as irrigation water. The result shows that the irrigation water reduced 50.7% and 86.2% for original demand in first and second crop after using new recycling water as the irrigation water.
