Assessment of irrigation and environmental quality at the hydrological basin level: II. Salt and nitrate loads in irrigation return flows

摘要: Abstract Irrigation return flows may induce salt and nitrate pollution of receiving water bodies. The objectives this study were to perform a nitrogen mass balance at the hydrological basin level quantify loads exported in drainage waters three basins located 15,500 ha irrigation district Ebro River Basin (Spain). main inputs outputs measured or estimated these along 2001 year. Groundwater inflows groundwater outflow one significant components balances. Thus, off-site impact ascribed solely was soil water. Salt concentrations low (TDS around 400–700 mg/l, depending on basins) due TDS presence salts geologic materials, inversely related fractions (DF = 37–57%). However, high DF, relatively (between 3.4 4.7 Mg/ha), although moderate compared other areas with more saline geological materials. Nitrate highest (77 mg NO 3 − /l 195 kg N/ha) III, heavily fertilized (357 kg N/ha), percentage corn shallow, retention flood-irrigated soils. In contrast, lowest (21 mg 23 kg found II, 203 kg N/ha preponderant deep, alluvial valley soils, crops N requirements (alfalfa pasture), non-cropped area (26% total) fertigation practices sprinkler-irrigated fields (36% irrigated area). 56% applied by fertilization lost as only 16% II. summary, efficiency coupled an inadequate management are responsible for low-salt, high-nitrate surface outflows from studied basins. consequence, higher efficiencies, optimized reuse key strategies better control district.