Profile of coastal basin: Po di Volano fresh water outflow and nitrogen and phosphorus discharge into brackish lagoon (Sacca di Goro-Po River Delta)

The time pattern, from 1973 to 1991, of fresh water inflow into the most southern Po river Delta bay (Sacca di Goro) was studied using water runoff records, continuously monitored by the 'Consorzi di Bonifica' (Basin Water Authorities). The Sacca di Goro watersheds are part of a coastal reclaimed territory, mostly below the mean sea level. The Po di Volano outflows analysis showed a seasonal pattern, direct consequence of a man-ruled regulation to drain the soil in autumn and winter and irrigate the fields in spring and summer. The nutrient concentrations in the main canal (Po di Volano), monthly monitored by the Provincial Government (Environmental Department), was also considered. Nutrient concentrations, from 1983 to 1991, show a decreasing trend for Phosphorus, no significant trend for Nitrogen compounds. Ammonia and nitrate concentrations vary following two different seasonal patterns. A rough estimate was computed for the amounts of Nitrogen and Phosphorus discharged by Po di Volano: higher amounts are carried in spring and summer in relation to the higher water flow. The results are discussed in relation to the hydraulic regulation of the basin and to the source of the nutrients, mainly coming from agricultural land