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    Water balance of Huacachina Oasis, Peru
    (Universidad Cientifica del Sur, 2024-07-01)
    The Huacachina oasis, on Peru’s south-central coast, is an important tourism hotspot, driving economic activity in the Ica region. However, its natural sustainability has been compromised by aquifer overexploitation, leading to a decline in the water table. Currently, it is grappling with water recharge challenges, and has been resorting to methods such as recharging water from wells. Despite its importance, there have been few studies of the water balance at the Huacachina oasis. The aim of this study was to investigate the hydrological balance of the oasis, scrutinizing both water losses and gains, including evaporation, infiltration and inflows. Over a 72-hour period, precipitation, water level fluctuations and inflow rates were recorded and validated. Evaporation was indirectly computed using the Penman method, which is known for its efficacy. The oasis's storage capacity was assessed using detailed bathymetric and topographic surveys. The study identified the lowest bottom elevation at 401.488 m.a.s.l., the highest at 404.194 m.a.s.l., and a storage capacity of 35,813 m3. Our results showed precipitation had no impact on water supply, with the main source being well water pumped from underground. Water losses were due mainly to evaporation and infiltration. Daily evaporation averaged 7.7 mm, while the infiltration rate stood at 0.55 mm/hr. Infiltration exceeded evaporation by 1.7 times (63.4% vs. 36.6%). A water imbalance of 11.5 % was identified, with water inflows exceeding outflows, probably due to leaks in water and sewage systems. Unlike previous research, this study provides a detailed temporal analysis of Huacachina oasis water dynamics; however, in the future additional research will be required to address limitations. Our study also emphasizes the need to explore hidden water sources (leaks in water and sewage networks), in order to address improved oasis management and the effects of climate change, and to ensure sustainability.
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    geeSEBAL-MODIS: Continental-Scale Evapotranspiration Based on the Surface Energy Balance for South America
    (Elsevier BV, 2023-12-07)
    Monitoring actual evapotranspiration (ET) is critical for the accurate assessment of water availability and water resources management, especially in areas with dry climates and frequent droughts. The Surface Energy Balance Algorithm for Land (SEBAL) has been used over several land and climate conditions, and is able to estimate ET at field scale with high accuracy. However, model complexity and subjective parameterization have hindered its operationalization, until the recent development of the geeSEBAL model, which implements the SEBAL model on the Google Earth Engine platform. Here, we present a unique methodology for a continental-scale application of SEBAL, called geeSEBAL-MODIS, that employs novel land surface temperature normalization techniques, enabling the application of contextual ET models to very large scales. We introduce a dynamic ET dataset for the entire South American continent, between 2002 and 2021, at 500 m spatial and 8 days temporal resolution. The satellite-based data were compared against daily ET measured at 27 flux towers as well as water balance-based annual ET from 29 large river basins. geeSEBAL-MODIS data were also compared to eight state-of-the-art global ET datasets. At local scale, geeSEBAL-MODIS demonstrated a satisfactory performance (correlation (r) = 0.65, Kling-Gupta Efficiency (KGE) = 0.64, Mean Absolute Error (MAE) = 0.83 mm day−1 (24.7 %) and Root Mean Squared Error (RMSE) = 1.07 mm day−1 (31.8 %)), with negligible bias. At basin scale, geeSEBAL-MODIS generally underestimated ET (bias = -85 mm year−1, r = 0.65, KGE = 0.47, MAE = 107 mm year−1 (10.1 %) and RMSE = 137 mm year−1 (12.9 %)). Compared to other global datasets, geeSEBAL-MODIS demonstrated better performance over multiple South American biomes, climates and land cover types. The developed dataset also provides lower errors (local monthly RMSE = 23.0 mm month−1 and basin annual RMSE = 138 mm year−1) and when compared to the performance of the global datasets (local monthly RMSE between 23.9 and 30.1 mm month−1 and basin annual RMSE between 161 and 308 mm year−1). The analyses demonstrate that geeSEBAL-MODIS can be used as a tool for monitoring climate change and human-related impacts on ET. The geeSEBAL-MODIS model opens the path for high accuracy global ET monitoring at moderate to high resolution, supporting advances in water resources management around the globe.
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    Actual y futura disponibilidad del agua en un contexto de inseguridad hídrica en la subcuenca de Parón, cuenca del río Santa, Perú
    (Pontificia Universidad Católica del Perú, 2024-04-16)
    Water security in Andean watersheds depends on adaptive water management in the face of glaciohydrological and socioeconomic impacts. The Parón sub-basin in the Santa River basin (Ancash, Peru) is a suitable case in this respect. Water is regulated by a floodgate in the Parón lake, which has become a focal point of social conflict. This study analyzes the water balance of this sub-basin using a semi-distributed hydrological model for the present (2006-2016) and future (2030-2050), considering different scenarios of precipitation variation, glacial melting, and increased water demand. Without regulation of the lake, the sub-basin would enter into a strong water deficit in the dry months (June-August). Until 2030 (2050), assuming a maximum regulation of 2.6 m³/s, a 15% (35%) increase in precipitation, and a 10% (26%) decrease in the glacier contribution to the annual flow, water availability would be reduced by 37% (35%). In a pessimistic scenario with a 15% (35%) decrease in precipitation, water availability would still be reduced by 47% (56%) annually. These results highlight the need to keep a socially acceptable minimum water flow (>2 m³/s) to avoid critical levels of water scarcity in the dry months and to address the needs of local water users.
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