以水旱混作灌溉用水模式探討地下水合理應用之研究－以彰化溪州為例

APPLYING MIXED CROP IRRIGATION WATER DEMAND MODEL ON REASONABLE APPLICATION OF GROUNDWATER-A CASE STUDY OF CHANGHUA XIZHOU

吳瑞賢(Ray-Shyan Wu) ； 劉宜軒(I-Hsuan Liu) ； 劉日順(Jih-Shun Liu)

《農業工程學報》 65卷4期 (2019/12) Pp. 62-80

https://doi.org/10.29974/JTAE.201912_65(4).0006

摘要

臺灣在氣候變遷的衝擊之下，即使年平均雨量達2,500mm，每逢枯旱期間，各用水標的間的競相移用，仍是農業灌溉水源需更加正視的問題，在新水源開發困難的限制下，如何在不造成環境影響並以現有水源加以適當利用，乃為當今主要的課題。本研究為探討地下水資源用於農業灌溉的合理性，以彰化農田水利會溪州工作站所轄三條圳幹線灌區為研究區域，其位於臺灣中部濁水溪沖積扇上游，灌溉水源除了利用降雨及渠道供水外，灌區內農民亦會抽取地下水進行灌溉。本研究利用2015年及2016年一期作水文條件，透過渠道供水量優先模式以水旱作面積比例0.7:0.3（水稻耕作面積約146公頃，旱作耕作面積約63公頃）情形下，模擬灌區之用水情況並探討灌溉用水情形，模擬結果顯示2015年一期作試驗灌區之平均地下水抽水深度為757.75mm，佔總流入量（降雨、渠道及地下水水源之總和）之35.91%。以輪區而言，地下水抽水深度由第一輪區逐漸增加，於第五輪區超過50%的總入流量。當渠道灌溉供水量不足時，自第三輪區起，地下水成為灌溉之主要水源；2016年一期作之地下水抽水深度為118.3mm，佔總流入量之8.12%，其主因為2016年一期作期間降雨分布較為平均且渠道灌溉供水充足，故對地下水之依賴程度較2015年一期作低。假設水稻田在無降雨日皆進行抽水灌溉的情況下，利用2015年一期作期間之實測入流值及水文資料進行模擬，結果顯示當水稻田於無降雨日逕行抽0.5小時之地下水灌溉時，模擬之一期作總出流量與實測出流量相近。以此模式模擬結果推估，實際上本試驗灌區為產水區，其於一期作產出之水量為7.39百萬公噸，提供灌溉餘水予下游灌區使用。

關鍵字

系統動力模式 ； 水旱混作 ； 灌溉系統 ； 地下水抽取

並列摘要

Under the impact of climate change, even the average annual rainfall of Taiwan reaches 2,500 mm, during the drought period, the competition between each goal of water demand is still a problem that needs to be more squarely addressed in agricultural irrigation water sources. Under the conditions of escaping environmental impact, proper use of existing water sources is a major issue today. In order to explore the rationality of groundwater resources for agricultural irrigation, this study takes the irrigation districts under the jurisdiction of the Chang-Hua Irrigation Association as the research area. It is located in the upper reaches of the Zhuoshui River alluvial fan in central Taiwan. The irrigation water source uses canal water supply in addition to rainfall. Farmers in the study area will also pump groundwater for irrigation. This study applied the hydrological conditions in the 1^(st) crop period of 2015 and 2016 to simulate the irrigation district under the scenario of paddy rice and upland crop area ratio of 0.7:0.3 (about 146 ha of rice cultivation and about 63 ha of upland crop farming area). The simulation results showed that the average groundwater usage in the 1^(st) crop period experimental irrigation area in 2015 was 757.75mm, accounting for 35.91% of the total inflow (i. e. the sum of rainfall, canal irrigation water and groundwater). In the case of the rotation area, the groundwater is gradually increased from the No.1 block to over 50% of the total inflow. When the irrigation water supply of the canal is insufficient, the groundwater becomes the main source of irrigation since the No.3 block; the groundwater usage in the 1^(st) crop period of 2016 is 118.3mm, accounting for 8.12% of the total inflow, which is mainly due to the 2016 issue. During the period, the rainfall distribution was relatively average and the canal irrigation water supply was sufficient, so the dependence on groundwater was lower than that in the 1^(st) crop period of 2015. Assuming that the paddy fields are pumped for irrigation without rain, the simulated inflow values and hydrological data during the 1^(st) crop period of 2015 are used for simulation. The results show that when the paddy fields are irrigated by pumping for 0.5 hours without rain. The total outflow of the simulation is similar to the measured out flow. Based on the simulation results of this model, in fact, the study area is the water production area, and the water produced in the 1^(st) crop period is 7.39 million tons, providing irrigation residual water to the downstream irrigation area.

並列關鍵字

System dynamic model ； Mixed paddy rice and upland crops ； Irrigation system ； Groundwater pumping