Effects of Changing Land Use from Agriculture to Forest on Stream Water Quality in a Small Basin in NW Spain

Monitoring was conducted in a basin with a history of agricultural pollution (mainly due to the spreading of livestock slurry) to evaluate the response of stream water ion concentrations to the change from agricultural land use to forest. We measured pH, electrical conductivity (EC), and major dissolved elements [phosphate (PO ₄) phosphorus (P), nitrite (NO ₂) nitrogen (N), nitrate (NO ₃) N, ammonium (NH ₄) N, silicon (Si), sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), sulfate (SO ₄), and chloride (Cl)] in the stream water during the period 1997–2002 at irregular time intervals. Median values were significantly greater in the agricultural period than in the forest period (P