César Pedrocchi

Relationships between landscape pattern, wetland characteristics, and water quality in agricultural catchments.

Water quality in streams is dependent on landscape metrics at catchment and wetland scales. A study was undertaken to evaluate the correlation between landscape metrics, namely patch density and area, shape, heterogeneity, aggregation, connectivity, land-use ratio, and water quality variables (salinity, nutrients, sediments, alkalinity, other potential pollutants and pH) in the agricultural areas of a semiarid Mediterranean region dominated by irrigated farmlands (NE Spain). The study also aims to develop wetland construction criteria in agricultural catchments. The percentage of arable land and landscape homogeneity (low value of Simpson index) are significantly correlated with salinity (r(2) = 0.72) and NO(3)-N variables (r(2) = 0.49) at catchment scale. The number of stock farms was correlated (Spearmans corr. = 0.60; p < 0.01) with TP concentration in stream water. The relative abundance of wetlands and the aggregation of its patches influence salinity variables at wetland scale (r(2) = 0.59 for Na(+) and K(+) concentrations). The number and aggregation of wetland patches are closely correlated to the landscape complexity of catchments, measured as patch density (r(2) = 0.69), patch size (r(2) = 0.53), and landscape heterogeneity (r(2) = 0.62). These results suggest that more effective results in water quality improvement would be achieved if we acted at both catchment and wetland scales, especially reducing landscape homogeneity and creating numerous wetlands scattered throughout the catchment. A set of guidelines for planners and decision makers is provided for future agricultural developments or to improve existing ones.

Effect of Wetlands on Water Quality of an Agricultural Catchment in a Semi-Arid Area Under Land Use Transformation

The reduction of nutrients and sediments from agriculturalrunoff by natural wetlands has been commonly accepted, buttheirrole in water quality improvement at the catchmentscale has been seldom studied, especially in irrigated catchments. This study aims to elucidate the effect of natural and recently created wetlands on stream water quality after the conversion of a catchment for irrigation purposes.Water quality andmorphometrical andvegetation-related variables weremeasured in 19 wetlands on a 750-ha agricultural catchment under semi-arid conditions in the Ebro basin(NE Spain). A pollution gradient was found, increasing from the wetlands located in the upper catchment to those in the lower catchment.Wetlands with the lowest degree of artificiality, measured asthe amount of human createdstructures(e.g., channel excavation, dikes), and higher plant richness hadthepoorest water quality, probablybecause they were in the lower catchment and their water contained more pollutants carried from agricultural and salinesoils upstream. Some of these wetlands also had the highest rates of sediment and N-NO3 retention, incontrast to more artificial wetlands, which exported nutrients and sediments. Less artificial wetlands could also provide ancillary benefits such as biodiversity enhancement or landscape heterogeneity improvement.

Scenarios for the management of aquatic bird communities and wetland restoration after intensive agricultural land use and extensive land use cover changes in semi-arid territories

5 paginas, 2 figuras, 3 tablas.-- Trabajo presentado al 30o Congreso del SIL celebrado en Montreal (Canada).-- Publicado como articulo en Verhandlungen IVL.