Determinação da demanda hídrica efetiva e potencial em sub-bacias hidrográficas do Rio Piracicaba (SP) para fins de planejamento e gestão dos recursos hídricos

Abstract

The growing water demand is a global concern, as water, when not used rationally, compromises its supply, which can cause several problems, such as water scarcity. The objective of this work was to determine the effective and potential water demand in four Pairs of morphometrically similar hydrographic sub-basins located in the Piracicaba River Basin (BHRP) in the southeastern region of the state of São Paulo, to contribute to the planning and management of water resources. The Water Demand of the Agricultural Sector (DHPa) was calculated through the values of irrigation needs of the crops (temporary and permanent) existing in the study area, made available by the platform “Technical Coefficients for Irrigated Agriculture”. To calculate the DHPa, the temporary crops were classified by stages of development (I to IV), using the Normalized Difference Vegetation Index (NDVI). The calculation of the Water Demand of the Livestock Sector (DHp) involved bibliographic research to identify the amount of water consumed by each species of animal, and also the in situ data collection for the census of the herds. With regard to Population Water Demand (DHpop), it was established based on the population estimate for each census sector using a demographic indicator, as well as on the average per capita water consumption. Industrial Water Demand (DHi) was determined by the volume consumed from surface and underground water abstractions duly regulated for industrial purposes within the limits of the study areas. In addition to calculating the water demands of the sectors, two Quantitative Water Balances (BHQs) were elaborated, the first was determined considering the effective water demand and the Surface Water Supply (OHS), and the second consisted of the relationship of OHS with DHPa in conjunction with the other demands, to verify the situation regarding the level of commitment of surface water resources in terms of irrigation. From the results, it is noted that for the first BHQ, Pair 4 was the one that showed the highest levels regarding the commitment of water resources. In the analysis of the second BHQ, the DHPa was decisive to frame the water resources in more restrictive levels in most of the days analyzed in the studied sub-basins. However, the SB(C) and SB(D) sub-basins that make up the Pair 2, presented the most critical situations regarding the level of water commitment, due to the exploitation of their water resources for the different activities developed. The methods adopted in this work can be easily adapted to determination water demand in other 4th order hydrographic sub-basins located in the Piracicaba, Capivari and Jundiaí River Basins (PCJ), as well as in distinct hydrographic regions of the country, since, most of the databases used have national coverage. The results may assist managers in the elaboration of public policies with a view to planning and managing water resources.