| 摘要: | 因受到氣候變遷的影響，水文因子之不確定性提高，故水資源的調度更顯重要，在台灣用水項目中，又以農業用水為最高，故本研究從農業用水著手，以桃園大圳第十支線作為研究區域，探討埤塘灌溉系統作為桃園地區內特有的農業灌溉方式，其作用不僅能對於田區供水進行輔助，更能在降雨時增加雨水蓄存的空間。本研究利用系統動力模式建立埤塘灌溉系統，使用實測之大圳引水量及降雨量進行模擬，並且以2017年一、二期作做為模擬時間，觀察不同埤塘操作下之埤塘調蓄能力以及各項水文因子之變化，由於2017年一、二期作分別具豐、枯水年的特性，故本研究針對一期作套入農業用水移轉之背景進行案例分析，估算在不影響田間作物生長的情況下，大圳可減供之比例；針對二期作以枯水年做為案例背景，模擬極端氣候條件下，灌區在不同埤塘操作方式下缺水的情形。
根據模擬結果顯示，在埤塘可正常供水的情況下，能夠有效減緩灌區缺水的情況，而埤塘部分調蓄將會導致埤塘溢流量的增加；在大圳減供的案例分析中，埤塘調蓄可在不影響灌區小組耕作的情況下減少60%的大圳供水；在枯水年的案例分析中，在不進行面積折減的情況下，無任一灌區小組得以維持正常耕作，而在進行80%的面積折減時，埤塘調蓄可維持全期作耕作。透過排除河水堰取水之影響，以埤塘效益水深(PBD)與灌區小組到達凋萎點天數進行分析，發現兩者具高度相關性，並且可得到迴歸式y=75.94x+22，其中，y為灌區小組到達凋萎點的天數，x為埤塘效益水深(PBD)。
關鍵詞：桃園大圳，埤塘灌溉系統，系統動力模式，水稻田
;The uncertainty of water resources system is getting worse due to climate change impact, which enhance the importance of water resources planning and management on regional and global scale. Agricultural water account for 70% of nation’s water usage, which can be managed more precisely and efficiently. In this study, a system dynamic model was used to establish a unique agricultural irrigation method called pond irrigation system in irrigated area of Taoyuan. It’s function was not only to assist the irrigation water supply, but also used for water storage during rainfall. No.10 Sub Canal of Taoyuan main canal is the major irrigation water supply. The system dynamic model was simulated for 1st and 2nd crop season of paddy rice in 2017. Canal water and precipitation was the major irrigation supply while pond irrigation was considered as secondary supply. The main objective was the analysis of pond irrigation system under various operating scenarios. The rainfall for 1st and 2nd crop season of 2017 have the characteristics of high and low, respectively. Therefore, both seasons were simulated separately. Based on agricultural water transfer, the 1st crop season estimated that the proportion of canal water supply can be reduced without affecting the growth of crops in the field while, the 2nd crop season, based on the low rainfall, simulated the water shortage of irrigation area under extreme weather conditions.
According to the simulation results, it was observed that at normal pond supply, it can effectively alleviate the shortage of water in the irrigation area. It also operates at its best operating capacity under normal condition in comparison to partial operation. In partial operation, pond has more overflow due to restricted pond water supply. The 1st crop season simulation result shows that the reduction of canal water supply up to 60% without affecting the farming area under normal operation, while during partial operation there is no reduction in channel water supply. In the 2nd crop season, no irrigation group can maintain normal farming without farming area reduction. It was analyzed that when 80% farming area is reduced, the pond operation can maintain the crop period water supply normally. The regression analysis indicated strong correlation between Pond Benefit Depth (PBD) and the number of days to wilting point (D) as shown in regression equation D=75.94PBD+22.
Keywords: Taoyuan Main Canal, Pond irrigation system, Vensim model, Paddy field |
