ANTICIPATED IMPACTS OF CLIMATE CHANGE ONRAINFALL EROSIVITY OVER NEPAL-猫眼课题宝

DOI：

10.3850/38wc092019-1264

发表时间：

2019-09

期刊：

38th IAHR World Congress - "Water: Connecting the World"

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Rocky Talchabhadel;Anil Aryal;M. Maharjan;Rajaram Prajapati;H. Nakagawa;K. Kawaike

在本文中，我们评估了气候变化（CC）对尼泊尔降雨侵蚀力的预期影响。土壤侵蚀是一个持续的地貌过程，降雨是其中一个积极的驱动因素。CC对土壤侵蚀过程的显著影响是降雨侵蚀力的变化，这是由于降雨模式、数量和强度的变化而引起的。研究对修正通用土壤流失方程（RUSLE）历史时间（1961-1990）、中期（50年代：2041-2060）和远期（70年代：2061-2080）的降雨侵蚀力进行了评估。在两个代表性浓度路径（RCP 4.5和RCP 8.5）下，使用WorldClim中选择的10个环流模式（GCMs）的集合进行预测分析。Wischmeier和Smith，（1978）的方法被用来估计降雨侵蚀力。本研究概述了降雨侵蚀力的变化（过去和预测），并讨论了对全国土壤侵蚀的潜在影响。降水变化率和由此产生的降雨侵蚀力在RCP 8.5下相对大于RCP 4.5。70年代，在rcp8.5条件下，年降水量预计增加8.1%。结果表明，在RCP 8.5条件下，未来较长一段时间内，高原地区年降雨侵蚀力比历史时间增加27.8%，高原地区增加17.76%，中山地区增加17.7%，斯瓦利克地区增加19.68%，塔莱平原地区增加16.5%。我们的研究表明，未来CC情景仅基于降雨侵蚀因子的影响将增加土壤侵蚀。Pandey 2015;Uddin, 2016)对尼泊尔不同地区进行了小尺度的土壤侵蚀估算，很少有国家尺度的研究（Koirala et al., 2019; Uddin et al., 2018）。然而，CC对土壤侵蚀影响的评价仍然缺乏。量化过去和未来降雨引起的土壤流失的影响对于确定CC下容易发生侵蚀的易感地区至关重要。本研究旨在估计在国家尺度上CC影响下的未来降雨侵蚀力（尼泊尔全国分析）。本研究的结果有望为决策者提供有效的土地利用规划和土壤保护。范围为150 - 2000 MJ毫米/公顷-1小时-1年-1。在国内进行的一些区域研究显示了年降雨量侵蚀力的不同值；Pandey等人（2015）基于卫星降雨计算年降雨侵蚀力，其中尼泊尔西部的年降雨侵蚀力范围为1000 - 5000 MJ毫米/公顷-1小时-1年-1。Chalise et al.（2018）估计该国西部中山小流域的年降雨量侵蚀力约为400 MJ mm / h -1 h -1 yr -1。Ban等人（2016）估计，在该国首都附近的一个小流域，r因子约为700兆焦耳毫米公顷-1小时-1年-1。该研究评估了历史时期的国家平均年平均降雨侵蚀力为3071.3 MJ mm ha -1 h -1年-1，高标准偏差为2243.9 MJ mm ha -1 h -1年-1，最小值为114.9 MJ mm ha -1 h -1年-1，最大值为20800.9 MJ mm ha -1 h -1年-1。历史时期（70年代RCP 8.5下）的地理平均年降雨量侵蚀力为：HM为569.2 (727.4)MJ mm ha -1 h -1年-1，UH为2511.3 (2957.5)MJ mm ha -1 h -1年-1，MH为4061.3 (4780.3)MJ mm ha -1 h -1年-1，SW为4730.4 (5661.7)MJ mm ha -1 h -1年-1，TP为4730.5 (5513.9)MJ mm ha -1 h -1年-1。这意味着年降雨侵蚀力预计将在HM增加27.8%，在UH增加17.76%，在UH增加17.7%

In this paper, we have assessed the anticipated impacts of climate change (CC) on rainfall erosivity over Nepal. Soil erosion is an ongoing geomorphic process for which rainfall is one of the active drivers. The significant effect of CC on the soil erosion process is the change in the erosive power of rainfall due to variations in rainfall patterns, amounts, and intensities. The study assesses rainfall erosivity of revised universal soil loss equation (RUSLE) historical time (1961-1990), mid future (50s: 2041-2060) and far future (70s: 2061-2080). Ensembles of ten selected General Circulation Models (GCMs) from WorldClim under two representative concentration pathways (RCP 4.5 and RCP 8.5) were used for projected analysis. Wischmeier and Smith, (1978)’s approach was used to estimate rainfall erosivity. This study provides an overview of changes in rainfall erosivity (past and projections) and discusses the potential impacts on soil erosion across the country. The rates of change in precipitation and resulting rainfall erosivity are relatively more under RCP 8.5 than RCP 4.5. During 70s, annual precipitation is projected to increase by 8.1 % under RCP 8.5. We found that the annual rainfall erosivities are expected to increase by 27.8% in high mountain, 17.76 % in upper hill, 17.7% in mid hill, 19.68% in siwalik, and 16.5% in tarai plain of the country in far future under RCP 8.5 with respect to historical time. Our study suggests the scenario of CC in the future will increase soil erosion based on just the effects of the rainfall erosivity factor. Pandey 2015; Uddin , 2016) on the estimation of soil erosion at a small scale have been conducted for different regions of Nepal and very few studies (Koirala et al. , 2019; Uddin et al. , 2018) at a national scale. However, assessment of CC impacts on soil erosion is still lacking. Quantifying the effects of past and future rainfall-induced soil loss is essential in identifying the susceptible areas prone to erosion under CC. The present study aims to estimate future rainfall erosivity under the influence of CC at the national scale (nationwide analysis of Nepal). The outcomes of this study are expected to be useful to policymakers for effective land use planning and soil conservation. ranging from 150 – 2000 MJ mm ha -1 h -1 yr -1 . Some regional studies carried out inside the country showed different values of annual rainfall erosivity; Pandey et al., (2015) computed annual rainfall erosivity based on satellite-based rainfall where annual rainfall erosivity ranges from 1000 – 5000 MJ mm ha -1 h -1 yr -1 in western Nepal. Chalise et al., (2018) estimated annual rainfall erosivity to be about 400 MJ mm ha -1 h -1 yr -1 in a small watershed in western mid-hill of the country. Ban et al., (2016) estimated R-factor to be about 700 MJ mm ha -1 h -1 yr -1 in a small watershed located near to the capital city of the country. This study assesses the country averaged mean annual rainfall erosivity for historical time period to be 3071.3 MJ mm ha -1 h -1 yr -1 with a high standard deviation of 2243.9 MJ mm ha -1 h -1 yr -1 varying from a minimum of 114.9 MJ mm ha -1 h -1 yr -1 to maximum of 20800.9 MJ mm ha -1 h -1 yr -1 . The physiographical averaged mean annual rainfall erosivities for historical time period (under RCP 8.5 for 70s) are 569.2 (727.4) MJ mm ha -1 h -1 yr -1 for HM, 2511.3 (2957.5) MJ mm ha -1 h -1 yr -1 for UH, 4061.3 (4780.3) MJ mm ha -1 h -1 yr -1 for MH, 4730.4 (5661.7) MJ mm ha -1 h -1 yr -1 for SW, and 4730.5 (5513.9) MJ mm ha -1 h -1 yr -1 for TP. It means annual rainfall erosivities are expected to increase by +27.8% in HM, +17.76 % in UH, +17.7%

ANTICIPATED IMPACTS OF CLIMATE CHANGE ONRAINFALL EROSIVITY OVER NEPAL

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