Mapping Evapotranspiration, Vegetation and Precipitation Trends in the Catchment of the Shrinking Lake Poopó

Abstract

Lake Poopó is located in the Andean Mountain Range Plateau or Altiplano. A general decline in the lake water level has been observed in the last two decades, coinciding roughly with an intensification of agriculture exploitation, such as quinoa crops. 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. In this study, we seek to build upon these earlier findings by analyzing an ET time series dataset of higher spatial and temporal resolution, in conjunction with land cover and precipitation data. More specifically, we performed a spatio-temporal analysis, focusing on wet and dry periods, that showed that ET changes occur primarily in the wet period, while the dry period is approximately stationary. An analysis of vegetation trends performed using 500 MODIS vegetation index products (NDVI) also showed an overall increasing trend during the wet period. Analysis of NDVI and ET across land cover types showed that only croplands had experienced an increase in NDVI and ET losses, while natural covers showed either constant or decreasing NDVI 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. This quantification provides essential information for the sustainable planning of water resources and land uses in the catchment. Finally, we examined the spatio-temporal trends of the precipitation using the newly available Climate Hazards Group Infrared Precipitation with Stations (CHIRPS-v2) product, which we validated with onsite rainfall measurements. When integrated over the entire catchment, precipitation and ET showed an average increasing trend of 5.2 mm yr−1 and 4.3 mm yr−1, respectively. This result suggests that, despite the increased ET losses, the catchment-wide water storage should have been offset by the higher precipitation. However, this result is only applicable to the catchment-wide water balance, and the location of water may have been altered (e.g., by river abstractions or by the creation of impoundments) to the detriment of the Lake Poopó downstream.

An Application of Improved MODIS-Based Potential Evapotranspiration Estimates in a Humid Tropic Brantas Watershed—Implications for Agricultural Water Management

“…The Mann-Kendall test is a non-parametric test and a frequently used method for assessing trends in time-series remote-sensing raster datasets [57,58]. This test in combination with Sen's slope estimator allows more precise detection of spatial variability of such trends and has been widely used to monitor the dynamics of ecological variables [59][60][61]. The computation was run using R platform, modifying the protocols for time-series raster image analysis from Pironkova et al, 2018 [58].…”

“…where Q is the slope, x j and x i are the values at time j and i, and N is the number of periods, showing the number of observations per year [61]. Likewise, the p-value raster indicates the probability estimates and the trend's significance-the smaller the value, the higher the statistical confidence.…”

Desertificación: nuevos enfoques para un viejo problema

“…En una de las regiones más áridas del mundo como es Atacama (Chile), el crecimiento de la población y la actividad minera están vaciando los preciados acuíferos de la zona (Rinaudo y Donoso 2019; Elshall et al 2020). Grandes lagos y mares, como el Mar de Aral en Uzbekistán, el Urmia en Irán o el lago Poopó en Bolivia, se han vaciado por una explotación agrícola insostenible (AghaKouchak et al 2015;Gross 2017;Wurtsbaugh et al 2017;Torres-Batlló et al 2020). El vertido descontrolado de fertilizantes y pesticidas y la intrusión marina ha contaminado acuíferos y lagunas costeras como el Mar Menor, con los efectos que todos hemos visto y que tanto nos han conmovido.…”

Spatio-temporal Evaluation of Gridded Precipitation and Evapotranspiration Products Over Balochistan Province in Pakistan

“…Many satellite-based rainfall estimates and as well as reanalysis datasets have recently been used in many studies to estimate P (e.g., Zambrano-Bigiarini et al, 2017;Nogueira et al, 2018;Beck et al, 2019a;Torres-Batllo et al, 2020), to evaluate extreme events (e.g., Katsanos et al, 2016;Gupta et al, 2020), and to characterize droughts (e.g., Satgé et al, 2017;Wu et al, 2019;Zambrano-Bigiarini & Baez-Villaneuva, 2019). These products include Artificial Neural Networks-Climate Data Record (PERSIANN-CDR; Ashouri et al, 2015), Tropical Rainfall Measuring Mission (TRMM; Huffman et al, 2007), Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS; Funk et al, 2015), Multi-Source Weighted-Ensemble Precipitation (MSWEP; Beck et al, 2017a;Beck et al, 2019b), and ECMWF Reanalysis 5 th Generation (ERA5; Hersbach et al, 2018) and so forth.…”