Rio Mannu di San Sperate, Sardegna
Size: 472.5 km²
The River Basin is the Rio Mannu di San Sperate at Monastir. The basin drains an area of 472.5 km2 and is located in the southern part of Sardinia. A streamflow gauge was installed at the basin outlet, Monastir (a small town 30 km north of Cagliari, the capital of the island), and collected measures from 1925 to 1963. A small reservoir is present at the basin outlet and is used by ENAS, an agency of the Regione Autonoma della Sardegna government managing water, to collect water for multiple uses.
The basin ranges in elevation from 62 to 842 meters above the sea level (m.a.s.l.) with an average of 295.5 m.a.s.l.. The headwaters of the main river channel is located in the mountains of Sette Fratelli (south-east of the basin), an area with higher elevation (up to 800 m.a.s.l.) and rugged terrain. The lower areas, closer to the outlet, have instead more gently topography and are part of the Campidano plain.
The basin is mainly covered by agriculture fields and grassland, while only a small percentage of its area is occupied by forests in the south-east of the basin. Small urban areas are also presented inside the watershed.
The soil in the mountainous part of the basin is classified as brown soils and lithosols on crystalline schists and quarzites. The lower areas are instead brown soils, regosols and vertisoils or marls, sandstones and conglomerates. The floodplain is characterized by alluvial soils, predominantly gravelly or sandy gravelly.
The yearly mean precipitation is about 700 mm, while the yearly mean depth of runoff is about 200 mm, resulting in a runoff coefficient of 0.28. The hydrological regime is characterized by wet periods from October to April, where more than 90% of the rainfall is accumulated, and very dry summers (May-September). The yearly average temperature is 16° C and snowfall very seldom occurs. As a result, the delay between rainfall and runoff is very low, so that the rainfall and runoff distribution across the year are the same. The groundwater provides a negligible contribution to the streamflow in the channel network.
The basin includes an Experimental Site located in the Azienda San Michele, that is an agronomic research field covering an area of 4.36 km2 and managed by AGRIS, a research agency of Regione Autonoma della Sardegna government. Part of the Azienda (approximately 2 km2) is located in a hilly area with Maquis shrubland vegetation that is also a center of wildlife animal restocking. In the Northeastern part, the Azienda is delimited by the San Michele hill. At the bottom of this hill, the Rio Flumineddu joins the Rio Mannu. The Azienda has been used for decades to investigate agricultural genetics for a more efficient farming of durum wheat in climatic conditions with frequent drought periods, such as the ENV.2009.1.1.5.2 No. 244151, cliwasec, DoW 01.10.2009 122 Sardinian ones. Nowadays, the experimental agricultural fields are destined to open-field Mediterranean cultivations, particularly important for the economy of the island. Water for irrigation is provided by the ?Consorzio di Bonifica della Sardegna meridionale? in the Ussana-Donori? district, with pipeline network of 6.5 km.