黄土丘陵沟壑区沟道土地整治对径流-泥沙-氮素排放影响的模拟研究

针对黄土丘陵沟壑区沟道土地整治工程对水资源和水环境的影响难以评价的突出问题和现实需要,通过不同雨强和不同沟道土地整治比例的模拟降雨试验,研究了沟道土地整治工程对地表和地下径流过程的影响,分析了地表和地下径流氮素排放对沟道土地整治工程的响应,探讨了沟道土地整治工程对降水分配和氮素排放的作用机制。结果表明:沟道土地整治能调节降水分配、拦截地表径流、促进降水向地下径流转化,降水分配的调节程度随沟道土地整治比例的增加而增加;与无整治工况相比,在不同的降水强度下,30%和60%的沟道整治平均将降水的地表径流、土壤持留和地下径流比例从62∶21∶17分别调整为45∶22∶33和27∶23∶50。沟道土地整治减少地表径流中泥沙、硝态氮和铵态氮的输出,却有增加地下径流中硝态氮输出的风险;60%的沟道土地整治分别降低地表径流泥沙输出69%~82%、铵态氮输出63%~74%、硝态氮输出31%~48%,增加地下径流中硝态氮输出160%~337%,对地下径流铵态氮输出无影响。

Simulation study on the effects of typical gully land consolidation on runoff-sediment-nitrogen emissions in the loess hilly-gully region

It is necessary but difficult to evaluate the influence of gully land consolidation on water resources and water quality in the loess hilly-gully region. Through the rainfall simulation experiments in different rainfall intensities and channel land consolidation ratios, this study evaluated impacts of gully land consolidation project on surface and underground runoff, analyzed responses of gully land consolidation project on nitrogen emissions and also discussed the mechanism of gully land consolidation on precipitation distribution and nitrogen emissions. Results indicated that the gully land consolidation project could regulate the distribution of precipitation, intercept rainfall runoff and promote the transformation of underground runoff. The regulation level increased with the increase of gully land consolidation ratio,and the average proportions of surface runoff, soil retention and underground residence from precipitation of different rainfall intensities can be adjusted from 62:21:17 to 45:22:33 and 27:23:50 when the gully land consolidation ratios were designed as 30% and 60% respectively. The gully land consolidation project reduced the discharge of sediment, nitrate nitrogen and ammonium nitrogen in surface runoff but with an increased risk of nitrate nitrogen output in groundwater runoff.The gully land consolidation with a proportion of 60% could reduce 69%~82% of sediment output, 63%~74% of ammonium nitrate output, and 31%~48% of nitrate nitrogen output in surface runoff, but increased 160%~337% of nitrate nitrogen output and had no effect on the ammonium nitrogen output in groundwater runoff.