台灣在農業用水方面，佔用水量最大宗的為水田灌溉部分，而現行輪區內水稻田轉作旱作作物已相當普遍，形成水稻、旱作混植之輪區，旱作種植則完全依循農民的意願，種類繁多，各作物的需水量、需水日期、栽種時間與栽培方式等灌溉條件各有不同，且由於目前台灣輪區的灌溉用水，多以人工操作配水，導致輪區之灌溉水量無法精密控管，在用水調配上仍有相當大的節水空間。本研究於彰化莿仔埤圳的三條圳幹線重劃區，以系統動力模式建立水稻、旱作混植輪區灌溉用水模式，透過精密灌溉的方式，調配灌溉所需用水，減少灌溉水的損失，提升農業灌溉效率。 透過水、旱田田間精密灌溉用水模式，進行精密灌溉用水計算，以2016年於試驗區調查旱作生長週期與抽水灌溉水量之關係，在旱田需水量模擬案例中以包心白菜為例，依模式灌溉配水能節省灌溉水深291 mm，約18.8萬噸的水量；水田部分，2015年二期作期間，進行30天灌溉需水量模擬，結果顯示若能依自動控制水門進行閘門開度調控配水，可省下灌溉水深519 mm，約78萬噸的水量。在輪區旱作混植的案例中，統計試驗區總旱作面積64.4 ha於2016年1月至4月，各輪區抽水灌溉平均用水深度為81 mm，總用水量約26萬噸，模擬灌溉平均需水深為65 mm，總用水量約21萬噸，若能依模式灌溉配水，平均能節省灌溉水深16 mm，約5萬噸的總用水量。在探討水、旱田不同面積比例下各作物需水量變化，以水稻、旱作(包心白菜、高麗菜)比例7:3與比例5:5混植為例，統計從2016年1月至4月最多可省下水深65 mm，約14萬噸的灌溉用水量，當灌溉水資源有限時，則可改變作物栽種策略，以不休耕的方式，達到節水灌溉之目的。 ;In Taiwan, irrigation water accounts for the major usage in agricultural water. Recently, mixed paddy rice and upland crops fields becomes more and more popular for farmers choose to grow crops based on their individual wills. Given the situation that in Taiwan irrigation water distribution depends on manual work, and the water of irrigation and the lost from the conveyance can not be accurately calculated, the supply and demand in the field is lack of coordination. This study applies system dynamic model to establish irrigation water management model for a mixed paddy rice and upland crops field in central Taiwan. The goal is to provide precision irrigation practice allocating irrigation water in such way to minimize water loss and raise efficiency. Through precision irrigation practice for mixed paddy rice and upland crops fields, a substantial saving in irrigation water, i.e., 291 mm in terms of water depth can be realized for one season of growing vegetable in 2016. In the case of paddy field, 519 mm of water saving was estimated for a 30-days simulation on the proposed automatic control gates system in the second rice crop on 2015. Moreover, in the test site, the pumped groundwater was estimated to be 81 mm in depth, which compared to the simulated water requirement 65 mm indicates the possible eater saving being 16 mm. The study on the possible water saving for 9 scenarios provides information in management the mixed crops farming in water shortage periods.
