水稻免耕对流域蓝绿水的影响

Effects of No-tillage of Rice on Blue and Green Water at Basin Scale

研究水稻免耕的水文效应对免耕技术的推广和农业可持续发展具有重要意义。然而,以往研究主要在站点尺度上,尚未阐明免耕对流域蓝绿水的影响。以湘江流域为试验区,利用2000年的土地利用、数字高程、土壤数据、农业管理数据和2000—2018年的气象数据驱动SWAT水文模型,模拟了水稻免耕对流域年蓝水(产水量+深层地下水补给量)和绿水(实际蒸散发+土壤含水量)的影响。研究结果表明:和传统耕作相比,水稻免耕引起深层地下补给量下降了5.62%,比产水量的高5.35%。但是蓝水的变化主要归因于产水量的变化,产水量对蓝水变化的贡献为72.46%。水稻免耕引起流域绿水流(实际蒸散发)减少了8.460×10^(7) m^(3),但绿水库(土壤含水量)的增加(14.543×10^(7) m^(3))抵消绿水流的减少,最终导致绿水总量增加。因此,水稻免耕影响蓝绿水的分配主要通过改变产水量和土壤含水量来实现。产水量主要影响蓝水变化,而土壤含水量主要影响绿水的变化。由于水文要素之间的相互抵消,水稻免耕对整个流域蓝绿水的最终影响并不大,但流域范围内的空间差异较大。水稻免耕提高了绿水在水资源总量中的比例,增加了农田生态系统的生态可用水量,因此具有积极作用。

It is of great significance to study the hydrological effect of no-tillage of rice for the popularization of no-tillage technology and the sustainable development of agriculture.However,previous studies were mainly conducted at station scale,and the effect of no-tillage of rice on blue-green water at basin scale is still unclear.Taking the Xiangjiang River Basin as the test area,based on the land use data,digital elevation data,soil data,agricultural management data in 2000 and meteorological data-driven SWAT model,this paper simulates the effect of no-tillage of rice on blue water(water yield+deep groundwater recharge)and green water(actual evapotranspiration+soil moisture content)in the basin.The results show that:Compared with traditional tillage,no-tillage of rice had a greater influence on recharge of deep groundwater,resulting in a decrease of 5.62%,which was 5.35%higher than that of water yield.However,the change of blue water was mainly attributed to the change of water yield,whose contribution was 72.46%.The green water flow(actual evapotranspiration)decreased by 8.460×10^(7) m^(3) due to no-tillage of rice,but the increase of green water reservoir(soil moisture content)offset these and eventually resulted in the increase of green water.Therefore,the change of blue-green water distribution under no-tillage of rice was mainly achieved by changing water yield and soil moisture content.The water yield mainly caused the change of blue water,while the soil moisture content mainly resulted in the change of green water.Due to the mutual offset of hydrological factors,there was no significant final effect of no-tillage rice on the blue-green water of the whole basin,but large spatial differences within the basin.No-tillage of rice increased the proportion of green water in the total water resources,and increased the ecological water available in the farmland ecosystem,so it played a positive role.