No abstract

The presence of impervious surfaces in catchments interferes with the natural process of infiltration, which has a marked influence on the hydrological cycle, affecting the base flow in rivers and increasing the surface runoff and the magnitude of flood flows. Like many Latin American cities, Loja (located in southern Ecuador) has experienced significant rates of urban growth in recent years, increasing the impervious surfaces in the catchment where it belongs. The aim of this study is to analyze the spatiotemporal dynamics of imperviousness in the study area for the period 1989–2020, using the Normalized Difference Impervious Surface Index (NDISI) and the supervised classification of Landsat images. The effect on flood flows was studied for each timestep using HEC-HMS hydrological model. Additionally, a future scenario of impervious surfaces was generated considering the observed spatiotemporal variability, possible explanatory variables, and logistic regression models. Between 1989 and 2020, there was an increase of 144.12% in impervious surfaces, which corresponds to the population growth of 282.56% that occurred in the same period. The period between 2001 and 2013 was the one that presented the most significant increase (1.06 km2/year). A direct relationship between the increase in impervious surfaces and the increase in flood flows was observed, reaching a significant variation towards the horizon year that could affect the population, for which measures to manage the surface runoff is necessary.

Water is essential for life and human activities. In addition to the constant increase in water demand, there are problems caused by inefficient governance, such as the discharge of untreated wastewater into rivers and seas, which is aggravated by the limited participation of civil society in decision-making. To face current and future challenges, solid public policies must be implemented, focused on measurable objectives, following planned and predetermined schedules on an appropriate scale, based on a clear assignment of functions to the competent authorities, and subject to periodic monitoring and evaluation. The Institutional Analysis and Development framework proposed by Ostrom made it possible to identify gaps in the existing governance, and to establish actions that could strengthen the institutional framework with the active participation of social actors, in order to achieve an effective conservation of water resources in southern Ecuador. The present study determined that regulations are not coherent with the conflict, the design of policies, and the effects of decision-making. The formal rules for wastewater management are not applied, and there is an incipient citizen participation, as well as disarticulation in institutions responsible for wastewater management. Recommendations were made to strengthen the institutional framework and governance of wastewater.

No abstract

The capabilities of images and products obtained by four satellite sensors with different spatial and temporal resolutions (LANDSAT 8, ASTER, MODIS and SENTINEL 3) were analyzed as inputs for the calculation of the reference crop evapotranspiration (ETo). The FAO Penman-Monteith equation was: (a) used in a traditional way, to calculate local values of ETo using data recorded in the existing meteorological stations in the study area; and (b) applied to estimate the regional ETo using the images and products obtained through remote sensing. The capabilities of the satellite products selected were evaluated by means of cross-validation, comparing the values obtained by the meteorological stations to the corresponding values extracted from the regional evapotranspiration maps. The coefficient of determination (R2), the Nash–Sutcliffe efficiency (NSE) and the root mean square error (RMSE) were calculated. The results of the study show that there is a direct correlation between the spatial resolution and the accuracy of the ETo estimates, the products of LANDSAT 8 being those that reached the greatest accuracy. Nevertheless, for continuous ETo monitoring, SENTINEL 3 is preferred.