Gift

Nitrogen (N) pollution in shallow groundwater within the Jianghan Plain—a depositional basin along the Yangtze River in China—is a serious issue affecting the local water supply. There is little concern regarding temporal variation patterns of groundwater N in regions with intensive groundwater/surface-water interactions thus far. In this study, a 2-year field monitoring program and a set of incubation experiments were jointly applied to characterize the seasonal variation mechanisms of groundwater N. Groundwater monitoring suggested that temporal N variations in monitoring wells of 25 and 10-m depth were correlated with fluctuations in water levels, with lower NH₄-N and higher NO₃⁻-N concentrations corresponding to groundwater discharge during the dry season, and with higher NH₄-N and lower NO₃⁻-N concentrations corresponding to groundwater recharge during the wet season. Batch sediment incubation experiments showed that buried organic carbon in sediments from the field site could not promote NH₄-N release, but exogenous organic carbon and oxidant input could catalyze organic N mineralization, resulting in NH₄-N release. Nevertheless, NO₃⁻-N release was limited in all incubations. Thus, the temporal variation patterns could be divided into (1) groundwater N in type-1 wells (25 and 10 m), controlled by the annual reversal of groundwater flow gradient, which determined whether there was input of exogenous organic carbon or oxidants, ultimately affecting organic N mineralization, denitrification and other transformation processes, and (2) groundwater N in type-2 wells (<4 m depth), which showed no significant seasonal variation, implying the process is mainly controlled by surface inputs in the shallower subsurface.

Meinzen-Dick Ruth Suseela, 'Mercados de agua subterránea en el Pakistán participación y productividad', , IFPRI, 1996 | En este informe de investigaciones, , se examina cómo funcionan los mercados de agua, quién participa, cuál es la naturaleza de las transacciones y qué efectos tienen los mercados en la productividad y el ingreso agrícolas, con objeto de determinar qué fomenta o impide el surgimiento de mercados de agua viables. En el informe se reseña la literatura actual sobre los mercados de agua subterránea, las pruebas empíricas de su funcionamiento y las opciones existentes en materia de política. Se examinan los patrones de establecimiento de pozos entubados y mercados de agua subterránea particulares, con datos de los distritos del país en general y luego se analiza con detalle el funcionamiento de los mercados de agua subterránea con datos de las familias campesinas recogidos en la encuesta realizada por el IFPRI de 1990 a 1992.