Capture and storage of pluvial water: an alterantive practice for arid-semiarid zone of La Pampa province (Argentina)

UMAZANO, A.M.; ADEMA, E.O.

Buenos Aires

Conferencia; International Conference "Environmental Change and Rational Water Use"; 2005

International Geographical Union

La Pampa is a mediterranean province localized between 35º S to 39º 20’ S and 63º 23’ W to 68º 17’ W. Water availability in west and south La Pampa strongly limits range production. Alternative strategies for a rational water survey and management are needed due to the arid-semiarid climate and scarcity of underground and surface aqueous resources of acceptable quality and amount. A possible solution for the problem is the harvest and storage of pluvial or meteoric water in dirt-tanks. The purpose of this project was to evaluate the potential to capture and storage of pluvial water (aptitude), as well as to asses the necessity of this alternative practice. The study was carried out in different geomorphic regions from west and south La Pampa with an annual mean precipitation bellow 500 mm. Isohyetal lines map was actualized until 2000 year, considering the pluviometric records of 36 localities with series longer than 20 years. This map established the northeast limit of study zone. Seven geomorphic regions were mapped using topographic, geologic and geomorphologic charts (Scale 1:100.000 to 1:250.000) considering direction and magnitude of slopes, absolute and relative altitudes and hydrography. Climatic (B1: annual mean precipitation), geomorphic (B2: topographic mean gradient, B3: soil permeability, B4: drainage, B5: surface material, B6: caudal of lotic waters and B7: salinity of lotic waters) and hydrogeologic (B8: caudal of aquifers and B9: salinity of aquifers) factors were used to classify the regions. In decreasing order of aptitude and necessity of capture and storage of pluvial water, the factors were qualified from 5 to 1. Using a matrix (rows: geomorphic regions, columns: factors), both aptitude and necessity were evaluated. For each region, arithmetic mean summarizes the possibilities of capture and storage of pluvial water and scarcity of conventional water resources. These means, called mean conditions, were classified as follow: very good (> of 4), good (4 to 3), fair (3 to 2) and bad (2 to 1). B1 values were taken from isohyetal lines map, B2 values were calculated from topographic charts, B3 and B4 values were defined from test-pits, B5 values were taken from geological charts, and B6 to B9 values were calculated from data of various authors. Finally, these regions were classified in decreasing order of aptitude and necessity of capture and storage of pluvial water, as follow: I) Lihuel Calel peneplain (good), II) modern floodplain (fair), III) sandy plain (fair), IV) mesas and depressions (fair), V) Colorado river fossil alluvial fan (fair), VI) Chical-Có plain (fair) and VII) basaltic plain (bad). This work found help for future research toward productivity increase for the zone with small environmental effect, intended a sustainable development.