Determination of water sources for underground structures flooding in MAr del Plata, Argentina.

BOCANEGRA, EMILIA M; MARTINEZ, DANIEL E.; CARRERA JESÚS; POOL MARÍA; FERRANTE, ANGEL

Krakovia

Congreso; XXXVIII Int. Assoc. of Hydrogeologists Congress. Groundwater Quality Sustainability; 2010

International Association of Hydrogeologists

Mar del Plata city, the main tourist resort in Argentina (Figure 1), registered a massive migration process during the second part of the last century, at a rate of 100,000 inhabitants each decade. During the rapid development of the city as a summer centre, most of the family houses placed near to the coast were replaced by buildings that include subsurface services, like parking lots, cellars or locker areas. Intensive groundwater exploitation led to an important piezometric level drawdown and seawater intrusion. The full approach consisted of the following steps: a) to identify the sources of recharge or end members, b) select the chemical species to be included in the geochemical balances, c) compute mixing ratios, and d) synthesis of results. In order to quantify the sources of increased recharge, a geochemical and isotopic survey was carried out on both potential end members and samples from underground structures leakage. As end members, five sources were identified: urban groundwater, water supply, sewage water, rain water and sea water intrusion. The resulting data were interpreted with the aid of code MIX (Carrera et al., 2004), which computes mixing ratios, while acknowledging uncertainties in end members. Results allowed computing the proportion of each water source in flooding urban underground structures in Mar del Plata. The average mixing ratios for leakage into underground structures are: runoff water 35%; sewage leakage 19%; rain water 30%; seawater 7%; and aquifer water, level rising 9%.