沟灌管理参数优化策略比较与最优灌水时间估算

Comparison of strategies for optimizing management parameters and estimation of optimal cutoff time for furrow irrigation

沟灌是中耕作物常采用的灌水技术,但灌水质量不高仍是目前存在的主要问题。为进一步提高沟灌灌水质量,该研究以在陕西省关中平原进行的45组沟灌试验为基础,结合数值模拟方法,量化比较了3种沟灌管理参数优化策略(策略1:仅对灌水时间优化;策略2:仅对入沟流量优化;策略3:同时对入沟流量与灌水时间优化)对灌水质量的提升效果,提出了适用于尾部闭合条件下的沟灌最优灌水时间简化估算方法。结果表明,策略3较策略1和策略2可更为明显地提高沟灌灌水质量;若仅从提高灌水质量的角度考虑,推荐采用策略3,若同时考虑优化策略的实用性,则推荐采用策略1。不同土壤入渗能力和灌水技术要素组合条件下最优灌水时间与水流推进至0.75倍沟长所需时间可采用线性函数表征,与所有验证组合模拟结果比较的平均绝对百分比误差为16.71%。采用该研究方法所得策略1和策略3条件下的最优灌水时间估算值与WinSRFR软件模拟结果基本一致,所有沟灌试验点平均绝对百分比误差分别为10.88%和12.00%。运用策略1和策略3条件下所得最优灌水时间估算值进行灌水质量模拟,综合灌水质量指标≥85.0%占有效沟灌试验点的比例分别为77.3%和90.2%,较现状条件下(64.4%)有明显提升,表明该研究对尾部闭合条件下沟灌最优灌水时间估算具有较强可靠性,可获得较高的灌水质量。该研究方法仅需观测水流推进至0.75倍沟长的时间即可估算尾部闭合条件下沟灌系统最优灌水时间,实用性较强,可为地面灌溉实时反馈控制系统提供理论基础。

Furrow irrigation has been one of the most commonly used approaches for crops, but with the low yield of irrigation water. In this study, 45 sets of experiments were conducted to further improve the performance of furrow irrigation in the Guanzhong Plain of Shaanxi province, China. Three optimization strategies of management parameters were quantitatively compared(Strategy 1: only optimize the cutoff time;Strategy 2: only optimize the inflow discharge;Strategy 3:simultaneously optimize the inflow discharge and cutoff time). A simplified method was proposed to estimate the optimal cutoff time for the closed-end furrow irrigation. The results show that Strategy 3 presented the best performance of the irrigation, followed by Strategies 1 and 2. The application efficiency, distribution uniformity, and storage efficiency for Strategy 3 increased by 20.5%, 10.6%, and 3.3%, respectively, and these increased by 13.8%, 4.1%, 1.1% and 6.8%, 9.3%,0.4% for Strategies 1 and 2, respectively, compared with the measured. More importantly, Strategy 3 was recommended only from the perspective of irrigation performance, but Strategy 1 was recommended when considering the practicability of the optimization strategy at the same time. A linear function was used to characterize the optimal cutoff time, optimal cutoff time,and the time when water advanced to 0.75 length of the furrow(T0.75L), where the determination coefficient of the function was 0.920, according to the different capacities of soil infiltration and the combinations of irrigation elements. The mean absolute percentage error was 16.71% between the simulated and estimated optimal cutoff time values. The Tcop values of Strategy 1and 3 were estimated by T0.75L, indicating fully consistent with the simulation using WinSRFR software. The mean absolute percentage errors of all furrow irrigation experiments were 10.88% and 12.00%, respectively. The indicators of irrigation performance were simulated with the optimal cutoff time under Strategies 1 and 3. It was found that the optimization values were lower than those in the simulation. But there were small declines of the application efficiency, distribution uniformity,and storage efficiency values, which were 1.0%, 4.0%, 3.5% and 4.0%, 4.8%, 4.1% for Strategies 1 and 3, respectively. In addition, the estimated optimal cutoff time values of Strategies 1 and 3 were used to simulate the irrigation performance, where the comprehensive irrigation performance indicator not less than 85.0%, accounting for 77.3% and 90.2% of the effective experiments, respectively, indicating an outstandingly higher than the current condition(64.4%). Therefore, this approach can be used to reliably estimate the optimal cutoff time values for the closed-end furrow irrigation, according to the time when water advanced to 0.75 length of the furrow, T0.75L. The finding can provide a strong basis to develop a real-time feedback control system in surface irrigation.