From 1950s to 1980s, various observational studies around the globe found a significant decrease in surface solar radiation (SSR), which reversed in late 1980s for most of the countries including India. SSR observations at 12 stations located across India revealed that a much stronger dimming has reappeared during the last decade (2006–2015) after a brightening during 1996–2005. In the present study, effects of renewed solar dimming on actual evapotranspiration and runoff were analyzed using a semi-distributed hydrological model, Soil and Water Assessment Tool (SWAT) in 24 river basins (ranging from 1260 to 40000 km²) located in peninsular India. For these river basins, calibration (2003–2009) and validation (2010–2014) were performed using the observed daily discharge data, obtained from water resources information system (WRIS) of India, with a 3 year warm up period (2000–2002). The sequential uncertainty domain parameter fitting algorithm (SUFI-2) of SWAT-CUP (calibration and uncertainty program) was used with modified Nash–Sutcliffe efficiency (MNS) as the objective function to calibrate 13 model parameters, which can potentially affect streamflow. In nearly all the river basins, the p- and r-factor of 95 percentage prediction uncertainty (PPU) were more than 0.7 and less than 1, respectively. At daily timescale, MNS values were more than 0.5 in most of the river basins, reaching up to 0.66 and 0.71 during calibration and validation periods, respectively. Calibrated model was used to analyze the water balance of these river basins and different sets of experiments (with observed SSR trends) were performed to find SSR impacts on it. The model was simulated with and without the observed declines in SSR trends. The average change in SSR (in terms of evaporation equivalent) was −267.93 ± 100.92 mm/day/year (−5.62 ± 2.12%) with maximum reaching up to −417.12 mm/day/year (−8.99%). Due to this SSR change, actual evaporation was reduced resulting in 18.97 ± 9.78 mm/day/year (4.13 ± 2.50%) change in percolation. The percolation changes were higher for river basins having areas covered by forests and cropland/woodland, and having loam and sandy-clay soils. The increase in runoff generated was 6.90 ± 3.42 mm/day/year (2.14 ± 1.58%) with a maximum of 15.25 mm/day/year (7.56%) whereas corresponding increase in streamflow was found to be 9.93 ± 5.27 mm/day/year(4.21 ± 2.38%) with a maximum of 26.71 mm/day/year (11.86 %). The study reveals that the recent observed SSR changes are significant enough to have resulted in increased streamflow in the monsoon dominated tropical river basins of India.

从 1950 年代到 1980 年代，全​​球的各种观测研究发现地表太阳辐射 (SSR) 显着下降，在 1980 年代后期，包括印度在内的大多数国家出现了逆转。在印度各地的 12 个站点进行的 SSR 观测表明，在 1996 年至 2005 年期间变亮之后，在过去十年（2006 年至 2015 年）中再次出现了更强的调光。在本研究中，使用半分布式水文模型、土壤和水评估工具 (SWAT) 在 24 个流域（范围从 1260 到 40000 km ²) 位于印度半岛。对于这些流域，校准（2003-2009）和验证（2010-2014）是使用从印度水资源信息系统（WRIS）获得的观察到的每日流量数据进行的，预热期为3年（2000-2002） ）。SWAT-CUP（校准和不确定性程序）的顺序不确定域参数拟合算法（SUFI-2）以改进的纳什-萨特克利夫效率（MNS）作为目标函数来校准13个模型参数，这可能会影响水流。在几乎所有流域中，95% 预测不确定性 (PPU) 的 p 和 r 因子分别大于 0.7 和小于 1。在每日时间尺度上，大多数流域的 MNS 值均超过 0.5，在校准和验证期间分别达到 0.66 和 0.71。校准模型用于分析这些流域的水平衡，并进行了不同的实验（观察到 SSR 趋势）以发现 SSR 对其的影响。该模型在有和没有观察到的 SSR 趋势下降的情况下进行了模拟。SSR 的平均变化（以蒸发当量计）为 -267.93 ± 100.92 毫米/天/年（-5.62 ± 2.12%），最大值达到 -417.12 毫米/天/年（-8.99%）。由于这种 SSR 变化，实际蒸发量减少，导致渗流变化 18.97 ± 9.78 毫米/天/年 (4.13 ± 2.50%)。对于森林和农田/林地覆盖面积以及壤土和沙粘土的流域，渗流变化较大。产生的径流增加 6.90 ± 3.42 毫米/天/年 (2.14 ± 1.58%)，最大值为 15.25 毫米/天/年 (7. 56%），而流量的相应增加为 9.93 ± 5.27 毫米/天/年（4.21 ± 2.38%），最大值为 26.71 毫米/天/年（11.86 %）。该研究表明，最近观察到的 SSR 变化足以导致印度季风主导的热带河流流域的流量增加。