Central Himalayan forested catchments provide fresh water supply and innumerable ecosystem services to millions of people. Hence, the understanding of linkages between forests and water is very crucial for availability and quality of water at catchment scale. Therefore, the present study aims to understand the hydrological response of two forested catchments (namely, Arnigad and Bansigad) in the Central Himalayan Region. Three-years’ data (March, 2008 to February, 2011) were collected from meteorological and hydrological stations in Arnigad and Bansigad catchments. The present paper describes the mean hydrological response of these forested catchments investigated through detailed field investigation. The annual hyetograph analysis revealed that the rainfall at both the catchments was highly seasonal, and wet-period (June–September) plays a key role in catchment functioning. Exceedance of rainfall threshold of ~ 200 mm (~ 10% of annual rainfall) significantly increased streamflow generation in both catchments. In Arnigad, the stream was perennial with a mean baseflow of ~ 83 mm per month (~ 6% of annual baseflow) whereas, Bansigad had greater seasonality due to lack of streamflow during the pre-wet-period (March–May). Separation of hydrographs in Arnigad and Bansigad catchments i.e. stormflow (6% and 31%, respectively) and baseflow (50% and 32%, respectively) helped to understand the probability of flooding during wet-period and drought during dry-period. The forest ecosystem in Arnigad displayed healthier hydrological functioning in terms of reduced stormflow (82%), and enhanced baseflow (52%), soil moisture (13%), steady infiltration rate (22%) and lag time (~ 15 min) relative to Bansigad. These enhanced values indicated soil capability to store water in the forested catchment (Arnigad) and helped to understand the volume of water (discharge) that was available during dry-period. The lower denudation rate at Arnigad by 41% resulted in decreased suspended sediment (18%) and bed load (75%) compared to Bansigad. Further, the enhanced dissolved solids in the Arnigad stream resulted from the higher organic matter generated in the forest floor. This study shows that rainfall during the wet-period was the main driver of hydrological functioning, whereas, forests provided substantial services by regulating water balance, soil moisture and sediment budget through different mechanisms of forest components at catchment-scale in the Central Himalayan Region.

中文翻译：

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印度喜马拉雅中部地区森林集水区的水文功能

喜马拉雅中部森林茂密的流域为数百万人提供了淡水供应和无数的生态系统服务。因此，了解森林与水之间的联系对于集水规模的水的可用性和水质至关重要。因此，本研究旨在了解喜马拉雅中部地区两个森林集水区（即Arnigad和Bansigad）的水文响应。从Arnigad和Bansigad流域的气象和水文站收集了三年数据（2008年3月至2011年2月）。本文通过详细的现场调查描述了这些森林集水区的平均水文响应。每年的湿度记录仪分析表明，两个流域的降雨都是季节性的，湿季（6月至9月）在集水区功能中起着关键作用。超过200毫米的降雨阈值（年降雨量的10％）大大增加了两个流域的水流产生。在Arnigad，该溪流是多年生植物，平均基流为每月〜83 mm（约占年度基流的6％），而Bansigad则具有较大的季节性，这是由于在湿润期之前（3月至5月）。分离阿尼加德和班西加德流域的水文图，即暴雨流量（分别为6％和31％）和基流（分别为50％和32％）有助于了解湿期和干旱期间洪水的可能性。就减少暴雨流量（82％），增加底流量（52％），增加土壤湿度（13％）而言，阿尼加德（Arnigad）的森林生态系统表现出更健康的水文功能。相对于Bansigad的稳定渗透率（22％）和滞后时间（〜15分钟）。这些增加的值表明土壤有能力在森林集水区（阿尼加德）储水，并有助于了解干旱期间可用的水量（排放量）。与Bansigad相比，Arnigad的剥蚀率降低了41％，导致悬浮泥沙（18％）和床荷减少（75％）。此外，Arnigad流中溶解固体的增加是由于森林地层中产生的较高有机物所致。这项研究表明，在雨季，降雨是水文功能的主要驱动力，而森林则通过喜马拉雅中部地区集水规模的不同森林组成机制，通过调节水平衡，土壤水分和沉积物收支来提供大量服务。