Integrated simulation of snow and glacier melt in water and energy balance‐based, distributed hydrological modeling framework at Hunza River Basin of Pakistan Karakoram region

Abstract

Energy budget-based distributed modeling of snow and glacier melt runoff is essential in a hydrologic model to accurately describe hydrologic processes in cold regions and high-altitude catchments. We developed herein an integrated modeling system with an energy budget-based multilayer scheme for clean glaciers, a single-layer scheme for debris-covered glaciers, and multilayer scheme for seasonal snow over glacier, soil, and forest within a distributed biosphere hydrological modeling framework. Model capability is demonstrated for Hunza River Basin (13,733 km 2 ) in the Karakoram region of Pakistan on a 500 m grid for 3 hydrologic years (2002)(2003)(2004). Discharge simulation results show good agreement with observations (Nash-Sutcliffe efficiency = 0.93). Flow composition analysis reveals that the runoff regime is strongly controlled by the snow and glacier melt runoff (50% snowmelt and 33% glacier melt). Pixel-by-pixel evaluation of the simulated spatial distribution of snow-covered area against Moderate Resolution Imaging Spectroradiometer-derived 8 day maximum snow cover extent data indicates that the areal extent of snow cover is reproduced well, with average accuracy 84% and average absolute bias 7%. The 3 year mean value of net mass balance (NMB) was estimated at +0.04 myr À1 . It is interesting that individual glaciers show similar characteristics of NMB over 3 years, suggesting that both topography and glacier hypsometry play key roles in glacier mass balance. This study provides a basis for potential application of such an integrated model to the entire Hindu-Kush-Karakoram-Himalaya region toward simulating snow and glacier hydrologic processes within a water and energy balance-based, distributed hydrological modeling framework.

Spatiotemporal patterns of High Mountain Asia's snowmelt season identified with an automated snowmelt detection algorithm, 1987–2016

“…1). Many of these catchments, such as the Tibetan Plateau, Tarim, Syr Darya, Amu Darya, and Indus, rely on snowmelt for more than 50 % of their yearly water budget (Bookhagen and Burbank, 2010;Shrestha et al, 2015). Many communities -particularly those at high elevations or those that depend on surface water for agriculture -are highly reliant on the timing of snowmelt.…”

“…To track the end of snowmelt, we leverage two additional datasets: (1) the raw Tb 37V time series, which rapidly increases as snowpack thins, and (2) a SWE time series calculated from the Tb 19 and Tb 37 GHz channels (Chang et al, 1987;Kelly et al, 2003;Tedesco et al, 2015;Smith and Bookhagen, 2016).…”

“…We leverage a combined time series of SSMI (1987SSMI ( -2009, Special Sensor Microwave Imager/Sounder (SSMIS) (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016), Advanced Microwave Scanning Radiometer -Earth Observing System (AMSR-E, 2002), AMSR2 (2012, and Global Precipitation Measurement (GPM, 2014(GPM, -2016 data, processed to 0.25 decimal degree (dd) resolution by interpolating raw PM swath data at a series of point locations as described in Smith and Bookhagen (2016) (see Supplement Table S1 for a full dataset listing). In essence, we group all measurements within a 0.125 dd radius of each point on a 0.25 dd grid and generate a spatially weighted mean value for each swath at that point.…”

Potential Impacts of Climate Change on Water Resources in the Kunhar River Basin, Pakistan

“…They used a Statistical Downscaling Model (SDSM), a combination of multiple linear regression and a stochastic weather generator, to downscale temperature and precipitation over the period of 2011-2099 under A2 and B2 scenarios of HadCM3, a global climate model. Different studies such as Akhtar et al [13], Ahmad et al [19], Shrestha et al [20], and Bocchiola et al [21] have assessed the impacts of climate change on the water resources of Pakistan [13,[19][20][21]. These studies were mostly conducted in the Upper Indus basin using hydrological models such as Snowmelt Runoff model (SRM), Hydrologiska Byråns Vattenbalansavdelning (HBV), Soil and Water Assessment Tool (SWAT), and the WEB-DHM-S model.…”

Hydrological Modeling of the Upper Indus Basin: A Case Study from a High-Altitude Glacierized Catchment Hunza

“…Many studies have been conducted to calculate the snow and glacier melt and their hydrological processes on watershed or river basin scales in the Upper Indus Basin (UIB). Tahir et al [2], Akhtar et al [11], and others [12][13][14] have overlooked discussing glacier behavior on river basin scale [2,6], except [15]. Some studies have been carried out for the long-term prediction of streamflow based on future climate scenarios by adding the future monthly precipitation and temperature changes simulated by General Circulation Models (GCMs) to the baseline precipitation and temperature data [2] but none have adopted multi-objective or multi-variable calibration approaches, with the exception of [16], who used different parameters to analyze internal consistency simulation of glacier mass.…”