Recursos hídricos subterrâneos em aluvião no semiárido nordestino: estudo de caso no Perímetro Irrigado Morada Nova, CE.

Abstract

Irregular rains and years of low rainfall are important factors that lead rural people to seek alternatives in order to guarantee water in their agricultural activity or even for domestic consumption. As a result, groundwater has gained importance, guaranteeing water security for small and medium-sized producers, with their exploitation through wells. The study was carried out in wells located on the Perimeter Irrigated Morada Nova, located in the municipalities of Morada Nova and Limoeiro do Norte - CE. Monthly static level readings of the wells were considered during the period from 2014 to 2019, relating them to the rainfall data for the same period, including years of low rainfall and indexes above the historical average for the region. Static level data were treated and organized in graphs to allow the observation of behavior during rainy and dry periods, in years with little rain and in more promising years. Iso depth maps with static level values and their respective coordinates were prepared in order to assess the depth of the water table in the region. The rise and depletion of each well over the course of the year was analyzed using the use and recovery coefficient, which was used in all years, taking into account the static level of the well at the end of the rainy and dry period. This coefficient allowed us to observe the well's recovery potential and, subsequently, how much the well depleted each year. The graphs showed a great drop in the static levels of the wells mainly in 2015, which was the lowest rainfall index during the study period, and the recovery of levels in 2018, the best rainy year; extending recovery to 2019. With the depth depth maps, it was possible to observe that the wells closest to the Banabuiú River had a higher static level during the rainy season and a greater level variation between the rainy and dry periods. The use and recovery coefficient made it possible to estimate how much was explored from the wells during each year, highlighting the year 2015 with the greatest depletion of the wells, with an average of 3.26 m and the coefficient value of 10.05, and the year 2016, with a coefficient of 12.95. The best coefficient, with the value of 0.58 and the average rise of the wells of 2.18 m were obtained for the year 2018. Such favorable indexes are justified by the occurrence of rains above the historical average of the region, which confirms strong collaboration and interference in rainy and dry periods, respectively.