Recently a natural reserve was created due to problems like: introduction of exotic species, illegal fishing and hunting, oil spils and wastewater dumps. The stress that these actions introduce in the ecosystem need, once again, to be evaluated with an interdisciplinary and integrated view: the PHES-system. Also in this area, a lot of partial studies have been done in the past, some of them by partners of this project. Different organizations of Bahía Blanca community were invited as stakeholders to take part of the implementation of ECOManage; local government, university and educational system, research canters, industrial and harbour consortiums, NGOs, and general public are interested to be active participants.

Bahía Blanca model domain bathymetry (top; source: IADO), main rivers and water bodies (bottom; INA, 2002)

Rivers
Sauce Chico, Saladillo and Napostá Grande Watershed areas are respectively 1620 km2, 830 km2 and 1260 km2. Both Sauce Chico and Napostá Grande rivers are originated in “Serra de la Ventana” in the top part of the watershed.
Sauce Chico and Napostá Grande rivers have monitoring stations in the end of their courses. Also both rivers have bifurcation close to the mouth of the rivers. In the case of Sauce Chico the Bifurcation is due to an irrigation channel. In the case of Napostá Grande the bifurcation is due to a hydraulic structure which diverts part of flow during extreme floods.

Watersheds of Sauce Chico, Saladillo and Napostá Grande obtained with SRTM topography

Flow and water quality stations in Sauce Chico river (source: Universidade Nacional del Sur)

 
Flow and water quality stations in Naposta Grande river (source: Universidade Nacional del Sur)

      
Water flow in Canal Maldonado in an extreme flood period. Picture taken in 18-4-2001 at 14:53 (source: IADO).

Urban and industrial sources
Wastewater treatment plants only have a primary treatment. Simultaneously IADO (2004) concludes that low oxygen values found near the wwtp discharge are related with waste wwtp discharges. Also ammonium and phosphate show values 10 times higher than the rest of the estuary.

Industrial areas around Bahía Blanca (source: Universidade Nacional del Sur).

Main Urban areas around Bahía Blanca estuary (source: Universidade Nacional del Sur) and WWTP - General Cerri, Bahía Blanca, Ingeniero White, Punta Alta (source: Matías et al., 2003)

 
Ports around Bahía Blanca estuary (source: Universidade Nacional del Sur)

Agriculture data
Main cultures in this area are wheat, sunflower and at a smaller scale barley for beer production (INTA-EEAB, 2002). This area is also suitable for 1 Livestock Unit per 5 to 10 hectares. Animal production is mainly bovine, with ovine production mainly for family consumption. Bovine production is mainly for beef and at a smaller extent milk production. Soils fertility in the area have decreased both due to soil use and also due to pedogenetic soil characteristics. To augment production, soil fertility is increased through the amendment of two critical nutrients: nitrogen and phosphorous. An increase in the use of these nutrients during last years has been detected by INTA-EEAB (2002).

Freshwater inputs
There are only two freshwater tributaries into the estuary, both entering from the northern shore. The most important is the Sauce Chico River that connects with the Principal Channel some 3 km downstream from the head. The Napostá Grande Creek reaches the estuary at about 1 km downstream of Ingeniero White Port. Although mean annual runoff for the Sauce Chico River and the Napostá Grande creek are low (1.9 and 0.8 m³ s^-1, respectively). Freshwater inflow from other creeks into the estuary is intermittent and only significant during periods of local precipitation.

Tides
The principal energy input into the Bahía Blanca system is produced by a standing, semidiurnal tidal wave. The propagation of the wave is affected by the geometry of channels.

Winds
Mid-latitude westerlies and the influence of the Subtropical South Atlantic High dominate the typical weather pattern of the region. The resulting circulation induces strong NW and N winds with a mean velocity of 24 km h^-1 .

Salinity and Temperature
Mean annual (13^oC), summer (21.6^oC), and winter (8.5^oC) surface water temperatures in the Principal Channel are always slightly higher at the head of the estuary, while mean surface salinity increases exponentially from the head to mid-reaches of the estuary. Longitudinal temperature distributions vary between rainy periods in spring‑summer and low runoff in winter, when the vertical thermal structure of the estuary is homogeneous and longitudinal variations are less than 3 ^oC . Depending on runoff conditions, salinity differences between the mouth and head of the estuary may reach 17 and more than 4 between surface and bottom. The partially mixed inner region between the mouth of the Sauce Chico River and Ingeniero White Port during normal runoff tends to become homogeneous at low runoff, while salinity patterns in the outer homogeneous region are similar to the adjacent continental shelf. The boundary between these regions depends on river discharge.