Analyses of landuse change impacts on catchment runoff using different time indicators based on SWAT model

Previous researches mainly focused on the runoff responses to landuse change based on annual, seasonal or monthly time scales, there are few studies based on daily scale. We conducted a comprehensive investigation into runoff responses on the daily scale as well as annual and monthly time scales using SWAT, and compared the impacts of time scales with different time indicators quantitatively. Jinjiang, a coastal catchment of southeast China with a humid sub-tropical climate, was used for simulations. A calibrated SWAT model produced satisfactory reproduction of annual, monthly and daily runoff processes over a nine-year (2002-2010) period at three gauging stations. Runoff was then simulated and compared using the same meteorological input but two different landuse scenarios (1985 and 2006, with reduced forest and increased cropland and urbanized area). The results showed varying change in runoff among three time scales and three catchments. The annual runoff had the smallest increase between two scenarios, monthly runoffs had medium rates (increasing in all months except October November), and daily runoff had the largest rates with the increase in flood peaks but decrease in drought flows, because of the variable influence on interception/evapotranspiration loss, percolation and antecedent soil water storage. Indicators of different time scales (annual runoff, monthly runoff, maximum 1-day and 5-day flood runoff, minimum 1-day and 7-day runoff) proved appropriate for analysing landuse change impacts. (C) 2015 Elsevier Ltd. All rights reserved.

以往的研究主要集中在基于年、季节或月时间尺度的径流对土地利用变化的响应，基于日尺度的研究较少。我们运用SWAT模型，对日尺度以及年、月时间尺度的径流响应进行了全面研究，并定量比较了不同时间尺度及不同时间指标的影响。本研究选取中国东南部湿润亚热带气候的沿海流域——晋江进行模拟。经过校准的SWAT模型对三个测站2002 - 2010年这九年期间的年、月和日径流过程再现效果良好。随后，利用相同的气象输入，但采用两种不同的土地利用情景（1985年和2006年，林地减少，耕地和城市化面积增加）对径流进行模拟和比较。结果表明，在三个时间尺度和三个流域中，径流变化情况各异。两种情景之间，年径流量增幅最小，月径流量增幅居中（除10月和11月外，其他月份均增加），而日径流量增幅最大，表现为洪峰流量增加但枯水流量减少，这是由于对截留/蒸散损失、入渗和前期土壤储水量的影响存在差异。不同时间尺度的指标（年径流量、月径流量、最大1日和5日洪水径流量、最小1日和7日径流量）被证明适用于分析土地利用变化的影响。（C）2015爱思唯尔有限公司。保留所有权利。