Hydrochemistry of the Springs

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The assessment of the water resources available in the Northeast Region, both in the surface springs and subterranean springs, is a valuable information for a number of sectors, either public or private, as water is a key and priority resource and is scarce in that region.

The first Hydrochemistry Map of the Subterranean Springs of the Northeast Region allows users to visualize the variations of drinkability, chemical types and possibilities of the agricultural use of the subterranean waters in the Northeast Region of Brazil.

The classes of drinkability are represented by means of hatchings and are grouped into brackets of drinkability that vary from good, regular, poor, bad, momentous to non-drinkable – those nearly always in sectors roughly coinciding with zones with lower rainfall and almost always associated with crystalline rocks.

The prevailing chemical types of water – mixed-chlorinated, calcium-bicarbonated, sodium-chlorinated, etc. – are represented by colors. The classification of the subterranean waters for use in irrigation is represented by symbols.

The map also brings an insert drafting the different types of aquifers in the Northeast Region, taking into account the set of geological attributes that establish the characteristics of the hydrogeological provinces of each system (sedimentary basins, coverages, metassediments and crystalline basis). This criterion is also used in the Explanatory Note, which describes the major general hydrochemical characteristics of these systems.

The Hydrochemistry Map of the Surface Springs of the Northeast Region surveys the general physical-chemical characteristics of the waters from major rivers and streams of the Northeast Region. It gathers information on the drinakability of the waters, the prevailing chemical types and also focus on their quality aiming at the use in irrigation. The classes of drinkability are also represented by hatchings, which establish six major brackets of drinkability. Each major chemical type of water is represented by a basic color, from which others of the same "range" derive from.

The Brazilian Northeast accounts for 18% of the total area of the hydrographic basins in the Brazilian territory, ranking in the third place among the five Major Regions, just behind the North and Central-West. The great diversity of the hydrological regimes of the Northeastern rivers comes from different rainfall conditions, from a number of physical characteristics – relative presence of sedimentary and crystalline rocks – and from the form of the hydrographic network, as well as from its morphology and vegetation. All this causes the variability of the water line annually drained.