Alteración hidrológica del barranco de Lerma (Zaragoza) por la transformación en regadío

Abstract

Irrigation expands without a real knowledge of its impacts and dynamics. This work aims to analyze changes in a natural creek’s hydrology as a consequence of receiving irrigation return flows from a newly-irrigated area. To this end, trends and seasonal patterns of flow, electrical conductivity and nitrate concentration were studied in Lerma creek (Zaragoza) from unirrigated conditions (2004) until the new irrigation area was completely transformed (2011). Irrigation resulted in an increase in flow (4.2 L/s year) and nitrate concentration (5.6 mg/L year) values. Although electrical conductivity decreased (-0.4 mS/cm year), the increase in flow resulted in an increase of the mass of salt exported from the area (232 kg/year). Irrigation management and hydro geological conditions produced annual, weekly and daily cycles of the studied variables. The results provided an insight on hydrological changes and their dynamics after implementation of irrigation, which should be taken into account for an adequate water resources management.

Runoff, nutrients, sediment and salt yields in an irrigated watershed in southern Navarre (Spain)

“…Similar observations have been reported in other pressurized irrigation districts in the Middle Ebro Valley (e.g., Isidoro et al, 2003;Causapé et al, 2012).…”

“…Both the intra-and inter-annual observed pattern can be explained by the influence of irrigation water in TDS concentration. The intra annual pattern is related to the dilution originated by irrigation water in spring-summer months (Causapé et al, 2012). On the other hand, during the study period Landazuria was a relatively recently transformed irrigated area (irrigation began in the year 1999) implemented over geological materials rich in gypsum and other soluble salts.…”

Modernization of new irrigated lands in a scenario of increasing water scarcity: from large reservoirs to small ponds

“…As a consequence, the drainage canals received much return water flows, in some cases by water loaded with nutrients (particularly nitrates) and salts. This increased the salt content in the main fluvial network (Lasanta et al, 2001;Isidoro et al, 2006;Isidoro and Grattan, 2011;Causapé et al, 2012), as has occurred in other irrigated lands in the Ebro Depression (Causapé et al, 2006). Thus, too much water was used, and nutrient and salt contamination occurred.…”

Interacciones montaña-llanura frente al cambio global: desafíos y oportunidades en la gestión del territorio y de los recursos hídricos en Riegos del Alto Aragón

“…Este último se elaboró en 1913 y fue aprobado en 1915, con el fin de regar 300.000 hectáreas, con un plazo de ejecución de 25 años, pero en la actualidad aún no puede darse por finalizado. Once años después de aprobado el proyecto de problemas: (i) provocaba un notable despilfarro del agua de riego, y (ii) producía gran cantidad de flujos de retorno o excedentes de riego, generalmente cargados de nitratos y sales por lixiviación del suelo (Lasanta et al, 2001;Causapé et al, 2006Causapé et al, , 2012Isidoro et al, 2006). Además, entre científicos y organizaciones ambientalistas subyacía la idea de que el gasto del agua y las inversiones realizadas en embalses y canales estaban sobredimensionados para el cultivo de cereales de invierno, incluso si la productividad había aumentado y se aseguraba una cosecha regular año tras año.…”