Mapping historical hydrological changes in the Lake Poopó catchment, Bolivia, with remote sensing
Creators: name: TORRES BATLLO, JUAN
Publisher: name: University of Surrey
Year: 2021

description: "Endorheic lakes are good indicators of climate variability. A great example is the Lake Poop´o, located in the Andean Altiplano. A general decline in the lake water level has been observed in the last two decades. Several factors have been linked with the shrinkage of the lake, including climate change, increased irrigation, mining extraction and population growth. Being an endorheic catchment, evapotranspiration (ET) losses are expected to be the main water output mechanism and previous studies demonstrated ET increases using Earth observation (EO) data. This dissertation seeks to build upon these earlier findings by analysing an ET time series dataset of higher spatial and temporal resolution, in conjunction with land cover, vegetation and precipitation data to monitor hydrological changes within the Desaguadero- Poop´o (DP) system.
description: Firstly, a spatio-temporal ET, precipitation and vegetation trend analysis was performed for the period 2002-2014, preceded by a validation of the hydrological satellite products. The results showed that changes in water losses occur primarily in the wet period within the central part of the DP system, while the dry period is approximately stationary. When integrated over the entire catchment, precipitation and ET showed an average increasing trend of 5.2 mm yr-1 and
description: 4.3 mm yr-1 respectively, suggesting that, despite the increased ET losses, the catchment-wide water storage should have been offset by the higher precipitation. Analysis of vegetation and ET
description: across land cover types showed that only croplands had experienced an increase in vegetation and ET losses, while natural covers showed either constant or decreasing vegetation trends together with increases in ET. The larger increase in vegetation and ET losses over agricultural regions, strongly suggests that cropping practices exacerbated water losses in these areas. A quantification of annual water losses per land cover type was carried out providing essential information for the sustainable planning of water resources and land uses in the catchment.
description: The last part of the dissertation focused on a long-term spatio-temporal precipitation trend analysis for the period 1981-2018. The assessment revealed that statistically significant increases in annual precipitation (2 - 6 mm yr-1) mainly occurred in the north and north-western part of the DP system. Only the southern part showed decreasing precipitation trends at a rate of -1 mm yr-1 while the central part did not show significant changes. Overall, a general increasing trend of about 2.5 mm yr-1 was observed for the entire DP system during the 38-year study period, with the months of December and February showing the highest significant increases.
description: The analysis of the onset and cessation times of the rainy season indicated a statistically significant decrease in its duration at a rate of -0.4 day yr-1 and an increment of the average precipitation intensity.
description: The results of this dissertation not only feature the capability of RS techniques to spotlight hy- drological disturbances in large and remote geographical areas but also provide a comprehensive assessment of hydrological changes within a water scarce region."