Simulation; Water quality; Hydric balance.

Water deficit is a reality in Brazil, even in regions where there is good water availability due to the pollution of water bodies. In this context, the Northeast region presents an additional aggravating factor, as, in addition to the irregular distribution of bodies of water, the region faces challenges such as high temperature and low rainfall, for most of the year. Therefore, the use of alternative sources of water supply becomes increasingly necessary. Of these alternatives, the use of rainwater stands out, which, on a recurring basis, is concentrated in some months of the year. Widely used in semi-arid regions due to low rainfall and the lack of conventional supply systems, rainwater can also be used in urban areas, directly impacting the mitigation of other problems, such as: flooding, landslides and congestion caused by excess rain. combined with the high waterproofing of the soil. To quantify and observe the impacts of the use of rainwater in urban areas, specifically in hill areas, three water supply-consumption water balances were carried out based on scenario simulations in Córrego da Telha, which is located in the neighborhood of little bird in the west of the city of Recife-PE. When carrying out the first water balance, the supply-consumption of water in a single residence was verified, where rainwater supply was considered in two time intervals: (a) annual interval from June 2021 to May 2022; and (b) interval with atypical precipitation in the months of May and June 2022. For the second and third simulation, water balances were calculated considering the entire hill basin and variables of the hydrological cycle: precipitation, surface runoff, evaporation, evapotranspiration and infiltration. What differentiates these simulations was the methodology for calculating surface runoff, for simulation 2 the rational method was used and for simulation 3 the SCS-CN method was used, both were carried out in programming language over a fortnightly period, being considered for the 1st period of study, atypical rains (accumulated value of 759.4 mm) and the 2nd period, typical winter rains (accumulated value of 172.5 mm). These simulations used information derived from mapping using remotely piloted aircraft (drones), which enabled the classification and quantification of the materials that make up the surfaces where precipitated water flows. Finally, the quality of the water supply to three houses located in the study area was monitored over 13 weeks. The simulation results indicated that rainwater supply could meet demand on 48% and 81% of days, respectively for intervals (a) and (b), with a corresponding percentage of water retention in the lot of 48% and 21% when analyzing simulation 1. For simulation 2, it presented the result of a reduction of around 12% in the volume of precipitation for the 1st study period (period of atypical rains) and 45% for the 2nd study period (rains traditional winter season). For simulation 3, the  simulations showed results of a 7% reduction in the volume drained from being released into the urban drainage network for the first study period (atypical rains) and around 39% for the 2nd study period (traditional rains). Regarding the quality of water used in the area under study, irregularities were observed in all residences. In a residence at the highest point of the hill, which receives regular supplies from the Pernambuco state company, the color parameter was within the permitted range, in just one collection. In the mid-slope residence, whose supply is mixed, receiving water from the company and other external sources, the presence of Escherichia Coli and/or total coliforms was detected in 2 collections, and while in the residence located in the foothills, which only has water supply from groundwater sources, there was the presence of Escherichia Coli and/or total coliforms in all weeks of the study. In this way, the use of rainwater can favor the region's water supply, alleviating supply inequality and mitigating urban problems.