半干旱区垄沟集雨系统点尺度土壤水分动态随机模拟

为揭示土壤水分动态对半干旱区垄沟集雨系统水文和生态过程的影响机理,基于Laio土壤水分动态随机模型(Laio模型),利用中国气象局定西干旱气象与生态环境试验基地2012—2013年垄沟集雨燕麦生长季根系层土壤水分观测数据及2000—2015年日降水资料,分析不同覆盖材料(生物可降解膜、普通塑料膜和土壤结皮)和不同沟垄比(30∶60,45∶60和60∶60cm)对生长季燕麦根系层土壤水分动态的影响,研究点尺度土壤水分概率密度函数特征,并对模型涉及参数进行敏感性分析。结果表明:研究区年降水的季节分配极不均匀,主要集中在5—10月份,占总降雨次数的66.6%;年降雨量的85.32%来源于10 mm的降雨,以暴雨为主;近16年研究区降水量呈缓慢增长趋势。生物可降解膜垄(BMR)、普通地膜垄(CMR)和土垄(SR)临界产流降雨量分别为1.35、0.95 mm和5.31 mm,平均集水效率分别为87.892%、94.203%和27.488%;在燕麦生长季,BMR和CMR的土壤含水量显著大于SR,SR的土壤含水量显著大于传统平作,各处理土壤含水量均服从正态分布;通过Laio模型模拟得到的各处理土壤水分概率密度函数的曲线特征(峰值及其位置、90%置信区间)及数字特征(期望、方差)与观测结果基本一致,CM指数均大于0.5,且可将集雨垄径流量作为单次降水的随机事件处理,说明该模型可应用于垄沟集雨系统土壤水分概率密度函数的模拟,为半干旱区农田水分高效利用管理提供理论依据。

Stochastic simulation of soil moisture dynamics at a point scale in a ridge-furrow rainwater harvesting system in a semiarid area

To determine the effects of soil moisture dynamics on hydrological and ecological processes in a ridge-furrow rainwater harvesting system in a semiarid area, a field experiment with a randomized complete block design was conducted, which evaluated the effects of different mulching materials (common plastic film, biodegradable mulch film and manually compacted soil) and different ridge-furrow ratios (30:60, 45:60 and 60:60 (cm:cm)) on soil moisture dynamics in the root zone of oats through model simulation and using the continuously monitored data of soil moisture during two consecutive oats growing years, 2012 and 2013, and daily precipitation from 2000 to 2015 at the Dingxi Arid Meteorology and Ecological Environment Experimental Station. The simulation was carried out using a stochastic model (Laio model) for soil moisture dynamics. The probabilistic density function (PDF) of soil moisture at a point scale was estimated using the Laio model, and the parameter sensitivity of the model was analyzed in this study. The results indicated that the precipitation distribution was irregular, and the precipitation events happening between May and October accounted for 66.6% of total annual precipitation events. Approximately 85.32% of annual rainfall received from rainfall higher than 10 mm. Annual precipitations had an increase trend in the past 16 years in this region. The threshold rainfall to produce runoff was 1.35, 0.95, and 5.31 mm for BMR (ridges mulched with biodegradable mulch film), CMR (ridges mulched with common plastic film), and SR (ridges with manually compacted soil), respectively, whereas the average runoff efficiency for the same treatments was 87.892%, 94.203%, and 27.488%. Soil water content for BMR and CMR was significantly higher than that for SR, which was significantly higher than that for traditional planting without ridges and furrows. The soil water content for all treatments followed a normal distribution. The curve characteristics (the curve peak value, position of the peak, 90% confidence interval) and the digital features (the expectations and variances) of the soil moisture PDF simulated by the model have a good consistence with observed values, and the consistency measure (CM) was higher than 0.5. The rainwater coupled with runoff in furrows could be considered a random event. The Laio model could be used for estimating the soil moisture PDF in ridge-furrow rainwater harvesting systems, and this could provide an insight for soil moisture management with a high use efficiency in semiarid regions.