Abstract
Abstract. The retreat of glaciers in the tropics will have a significant impact on water resources. In order to overcome limitations with discontinuous to nonexistent hydrologic measurements in remote mountain watersheds, a hydrochemical and isotopic mass balance model is used to identify and characterize dry season water origins at the glacier fed Querococha basin located in southern Cordillera Blanca, Peru. Dry season water samples, collected intermittently between 1998 and 2007, were analyzed for major ions and the stable isotopes of water (δ18O and δ2H). The hydrochemical and isotopic data are analysed using conservative characteristics of selected tracers and relative contributions are calculated based on pre-identified contributing sources at mixing points sampled across the basin. The results show that during the dry-season, groundwater is the largest contributor to basin outflow and that the flux of groundwater is temporally variable. The groundwater contribution significantly correlates (P-value=0.004 to 0.044) to the antecedent precipitation regime at 3 and 18–36 months. Assuming this indicates a maximum of 4 years of precipitation accumulation in groundwater reserves, the Querococha watershed outflows are potentially vulnerable to multi-year droughts and climate related changes in the precipitation regime. The results show that the use of hydrochemical and isotopic data can contribute to hydrologic studies in remote, data poor regions, and that groundwater contribution to tropical proglacial hydrologic systems is a critical component of dry season discharge.
Highlights
In the tropics, mountain glaciers and seasonal snow pack are an important part of the hydrological cycle as they form the headwaters for hydrologic systems that provide water to some of the most populated areas on earth (Nogues-Bravo et al, 2007)
While providing critical hydrologic functionality, glaciers are threatened by ubiquitous recession (Barry, 2006; Kaser et al, 2006; Vuille et al, 2008) that will cause significant hydrologic changes, including a reduction in dryseason water discharge (Barnett et al, 2005), an increase in peak discharges (Mark and Seltzer, 2003), and a general decrease in water resources in Asia, Europe, and the Americas (IPCC, 2007)
Modeling tropical pro-glacial hydrology is important for predicting the future impact of glacial retreat on water resources, but is difficult because of the relatively poor, location specific, understanding of hydrological processes in these remote areas
Summary
Mountain glaciers and seasonal snow pack are an important part of the hydrological cycle as they form the headwaters for hydrologic systems that provide water to some of the most populated areas on earth (Nogues-Bravo et al, 2007). Modeling tropical pro-glacial hydrology is important for predicting the future impact of glacial retreat on water resources, but is difficult because of the relatively poor, location specific, understanding of hydrological processes in these remote areas. In addition to glacial melt input, tropical pro-glacial hydrology must include surface and subsurface drainage systems. There is extensive research on understanding glacier dynamics in the tropics and modeling gross runoff, there has been very little research focused on the role of groundwater in these systems (Favier et al, 2008; Wagnon et al, 1998). The consequence is that existing proglacial hydrological models frequently oversimplify the input of groundwater to the hydrologic budget (Hood et al, 2006)
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