宁夏中部干旱带砂土混合覆盖下土壤蒸发估算

为寻求一种能够有效估算宁夏中部干旱带压砂地土壤蒸发量的方法,通过微型蒸渗仪大田试验,研究了0(S1),20%(S2),40%(S3),60%(S4),80%(S5),100%(S6)6种砂土混合比条件下土水蒸发比与表层土壤含水量的关系,并构建了压砂地土壤蒸发量估算模型。结果表明:土水蒸发比随表层土壤含水量呈分阶段变化,即S2~S6为2个阶段,S1为3个阶段,且S1第2,3阶段与其余处理相比存在一定滞后性,表层土壤含水量临界值可用砂土混合比表示为θ_si=0.0030s_i²-0.1705s_i+14.7340;S1~S6土壤蒸发量在第1,2阶段分别可用E_s=E₀(a_iθ_i+b_i),E_s=E₀(a_iθ_i²+b_iθ_i+c_i)进行表示(其中,S1第2,3阶段均为E_s=E₀(a_iθ_i²+b_iθ_i+c_i)),且整体精度达85%以上;在此基础上进一步综合水面蒸发量、表层土壤含水量及砂土混合比分两阶段构建了二次抛物面模型及多项式模型,模型整体可靠性较高,可为当地水资源管理提供参考。

Estimation of Soil Evaporation Under Mixed Sand Cover in Arid Regions of Central Ningxia

In order to find a method that can estimate the soil evaporation of gravel-mulched land in arid regions of central Ningxia effectively, the relationship between soil water evaporation ratio and surface soil water content under six sand-soil mixing ratios of 0 (S1), 20% (S2), 40% (S3), 60% (S4), 80% (S5), and 100% (S6) was studied, and the estimation model of soil evaporation of gravel-mulched land was constructed by setting up micro-lysimeters. The results indicated that the soil water evaporation ratio changed in stages with the surface soil water content, that was, S2~S6 had two stages, S1 had three stages, and there was a certain lag in the second and third stages of S1 compared with other treatments. The critical value of surface soil water content could be expressed as θ_si=0.0030s_i²-0.1705s_i+14.7340; The first and second stages of soil evaporation of S1~S6 could be expressed as E_s=E₀(a_iθ_i+b_i) and E_s=E₀(a_iθ_i²+b_iθ_i+c_i), respectively, (the second and third stages of S1 were E_s=E₀(a_iθ_i²+b_iθ_i+c_i)), and the overall accuracy was above 85%. Based on the above, the quadratic paraboloid model and polynomial model were constructed in two stages by further integrating water surface evaporation, surface soil water content, and sand-soil mixing ratios. The reliability of the model was high, and it could provide reference for local water resources management.