Maria Marlúcia Freitas Santiago

Water Resources of Ceará and Piauí

Most parts of Ceara and southeastern Piaui are part of the “drought polygon”, where potential evaporation by far exceeds precipitation. A mean annual rainfall of about 900 mm competes with a potential evaporation of 2200 mm powered by 3000 h of sunshine. Real evapotranspiration is of the order of 700 mm (SUDENE 1980; corresponding to 78% of rainfall), leaving only about 120 mm (13%) for runoff and 80 mm (9%) for percolation. Specific runoff in the region is of the order of 4 L/s/km2 to be compared with 21 L/s/km2 for all of Brazil (Barth et al. 1987). Mean annual temperature ranges from 19 to 29 °C. Koppen/Guettner-Kutzbach climate classification is “BS” for the focus areas of WAVES (Picus and Taua) whereas northern Piaui and northwestern Ceara are “AW”. Climate details, areal and temporal distribution of parameters may be found in Werner and Gerstengarbe (this Vol.) and Gerstengarbe and Werner (this Vol.). Here, we shall restrict our description to basic climatic features that define the general framework.

Investigations on Water Management and Water Quality in Picos/PI and Tauá/CE

The WAVES program (Water Availability, Vulnerability of Ecosystems and Society in Northeastern Brazil) aims at creating a knowledge base and strategies for sustainable development for the drought-prone northeast of Brazil. The perspective of climate change in a semiarid area with marginal water supplies requires strategic measures in order to avoid or at least mitigate severe water scarcity problems. Water scarcity results from the imbalance in a tripartite system between (1) the availability of natural resources with specific hydrochemical characteristics, (2) the state of development of water supply structures, and (3) water demand for specific uses. Seen trom such a perspective, it is obvious that water quality is an important and integral aspect of water availability. Hence, the analysis of water availability needs to integrate quantitative and qualitative studies.

Cluster analysis and geochemical processes for the characterization of the aquifer system in Maracanã/São Luis/MA

To better know the aquifer system in the Maracana Environmental Protection Area were collected samples in four campaigns; the first during the drought season and the others in the following rainy one. The water samples were analised for eleven hydrochemical parameters, CE, Ca2+, Mg2+, Na+, K+, Cl-, SO42-, HCO3-, NO3-, Fe and P. Cluster analysis separated the wells in the area, identifing three different groups that exploit water with electrical conductivity in the ranges of 230 to 400 μS/cm, 87 to 210 μS/cm, and 22 to 64 μS/cm, respectively. Data show a predominance of sodium chlorinated water. With these results and identification of geochemical processes determined by changes in concentrations of Fe and P it was possible to develop a model that identifies the aquifer of the aquifer system exploited by each well.

Factor Analysis in the Study of Geochemical Processes in the Apodi Sedimentary Basin, Northeast of Brazil

Wells of the Jandaira aquifer (in the Northeast of Brazil) were sampled for analyses of Ca, Mg, Na, K, Cl, SO4 , HCO3 , CO3 , NH4 , NO2 , NO3 , Fe, pH, hardness, and electric conductivity (EC). 87 wells were sampled during the dry season of 2009 and during the rainy season of 2010. R-mode factor analysis was applied, using WINSTAT software and the centroid method and Varimax rotation, for the identification of interrelations between the parameters studied. Variables that contribute significantly to the principal factor during both dry and rainy season are Cl, EC, hardness, Na and Mg; K plays a role during the dry season only and CO3 2during the rainy season. It is seen that, in general, recharge to the aquifer reduces the load of the two principal factors in favor of the others. R-mode factor analysis emphasizes the seasonal changes that occur, even when they are too small to be detected in the individual results of chemical analyses on the large compound of samples.

Groundwater as Indicator for Paleoclimatic Change in the Northeast of Brazil

The Earth’s paleoclimate is not only a subject of human curiosity about the past, but has also become a matter of “understanding the past for predicting the future”. With the Earth facing the threat of a man-made global change in climate, caused by the “greenhouse effect”, the history ofthe world’s climate has found new interest. Science needs large-scale global as weH as specific regional values for the calibration of models designed to foresee and quantify future changes in climate. (Such as CLIMAP — Climate: Long Range Investigation and Prediction, CLIMAP 1981). As instrumental meteorology reaches back to the seventeenth century only (based on the invention of the thermometer by Galileo, around 1590, and of the barometer by Torricelli, in 1643), paleoclimatic evidence for remoter periods has to be based on indirect measurements (“proxy data”), analyzing the advance and retreat of glaciers, the stratification of loamy soils (varves), the width of annual growth-rings of trees, pollen as indicator for vegetation, historic records (for taxing normally) of crop yields, or the isotope composition of marine deposits, etc. Within this last category, the 18O/16O ratio of these stable oxygen isotopes is of special importance.