For climate change scenarios, there is a high degree of complexity, with impacts on the future availability of water resources. In this context, studies related to changes in rainfall time series are essential in order to identify environmental vulnerability. The objective of this study was to analyze trends in the rainfall regime, number of rainy days and temperature for stations located at different continentality and altitude conditions in Northeast Brazil. Meteorological data of the Instituto Nacional de Meteorologia were used, being classified according to the location in relation to the continent: coastal strip (14 stations), strip of 150-300 km up to 300 m altitude (14 stations) and above 300 m (five stations), between 400 and 600 km from the coast up to 300 m (four stations) and above 300 m (eight stations). All the 45 stations used have a historical series with a data period of more than 30 years. The trend of rainfall and rainy days was obtained through the Mann-Kendall and regression analyses, at significance levels of 0.01 and 0.05, respectively. There were trends of reduction in the number of rainy days, in the coastal strip, as well as reduction in rainfall and rainy days, both in the strip of 150-300 km from the coast and in the Sertão region, with no significant effect of continentality in the strip of 400-600 km from the coast. For temperature, except for Maceió, AL, Brazil, there is a trend of increase in near future.

Understanding small-scale hydrologic processes and the impact of soil conservation techniques are crucial in reducing runoff and sediment losses in semi-arid regions. This study was conducted in the Alto Ipanema River Basin, in Pernambuco State (Brazil). Soil and water dynamics were intensely monitored in twelve experimental plots with different coverage conditions (plot with bare soil—Bare; plot with natural vegetation—Natur; plot with mulch—Mulch; plot with Cactus Palma—Palma). By far, bare soil conditions produced higher runoff and soil losses. Mulch cover was close to natural vegetation cover, but still presented higher runoff and sediment losses. Palma, which is a very popular spineless cactus for animal feed in the Brazilian semi-arid region, presented an intermediate hydrologic impact in controlling runoff, enhancing soil moisture, and also reducing soil losses. Experiments were conducted in one hydrologic year (2016/2017) at three different sites. They were intensely monitored and had the same number of plots. This enabled us to carry out a robust performance assessment of the two soil conservation practices adopted (Mulch and Palma), compared to natural vegetation cover and bare soil conditions. Such low-cost alternatives could be easily adopted by local farms in the region, and, hence, improve soil reclamation and regional resiliency in a water-scarce environment.

RESUMOO estudo das condições climáticas da região de Petrolina se faz necessário devido sua importância no cenário agrícola nacional. O objetivo do trabalho foi caracterizar os perfis pluviométricos, classificar por meio da utilização de técnica quantílica e a realização de balanço hídrico para diferentes regimes hídricos observados. Foram utilizados da estação meteorológica convencional (OMM: 81991) localizada no município de Petrolina-PE, os dados de precipitação pluvial e temperatura média do ar condensada. Além do uso da técnica de Quantis que classifica os anos de acordo com o índice pluviométrico anual como muito seco, seco, normal, chuvoso e muito chuvoso, foi utilizado o balanço hídrico pelo método de Thornthwaite e Mather. Na caracterização pluviométrica observou-se um quantitativo anual, variando entre 107,20 e 1023,50 mm, com média de 496,83 mm, a cada dois anos é possível observar uma precipitação pluvial igual ou inferior a 462,92 mm. Ao avaliar o balanço hídrico para os distintos regimes pluviométricos obtidos, pode-se verificar que todos os regimes pluviométricos apresentaram uma deficiência que se estende por todo o ano, com exceção para anos chuvoso e muito chuvoso que apresentam reposição nos meses iniciais do ano. Palavras-chave: ciclo hidrológico, climatologia, planejamento agrícola LOPES, I; GUIMARÃES, M. J. M.; MELO, J. M. M.; RAMOS, C. M. C. WATER BALANCE FOR PRECIPITATION REGIMES IN THE PETROLINA, PE REGION ABSTRACTThe study of the climatic conditions of the Petrolina region is necessary due to its importance in the national agricultural scenario. The objective of this work was to characterize the rainfall profiles, to classify by means of the use of quantile regression technique and the achievemnt of water balance for different water regimes observed. Data for rainfall and average temperature of the condensed air were provided by the conventional meteorological station (OMM: 81991) located in the city of Petrolina, PE. In addition to the Quantis technique, which classifies years according to the annual rainfall index as very dry, dry, normal, rainy and very rainy, the water

Abstract. Hydrological studies in small basins are essential for investigating the role of distinct processes on water resources conservation and to assess the impact of the natural ecosystems on improving water security especially in semiarid environments. In Brazil, the cooperative hydrological Network REHISA (“REde de HIdrologia do SemiÁrido”) comprises hydrologists from several universities of Brazil, focusing on field measurements, monitoring and modeling activities in well instrumented experimental rural catchments located at different regions and biomes in Semiarid environment. Water scarcity is a common aspect among the catchments, as well as risks of soil and water degradation. The objective of this work is to present assessments of near surface soil moisture spatial-temporal distribution, and to evaluate the impact of soil conservation techniques in reducing runoff, using small-scale experimental plots in a representative catchment of the Pernambuco State, Brazil. The study catchment is located in Alto Ipanema River Basin (AIRB) (with an area of 150 km2), which is located at the semiarid region of the São Francisco River (area of 641 000 km2). Soil and water monitoring was performed in experimental plots with different soil cover conditions (Bare soil plots; Plots with natural cover – Caatinga Biome vegetation; Plots with cactus Palma barriers; and Plots with mulch cover – Dry grass mulch at 4 t ha−1), where probes were installed for high resolution soil moisture assessment. In addition, regular soil moisture monitoring campaigns were conducted at 7 different locations, using a capacitance probe, with arboreal and shrub Caatinga vegetation, pasture and bare soil, predominantly Brachiaria decumbens. Mulch cover runs close to the Caatinga cover, but still with higher runoff generation, and presenting lower soil moisture temporal mean values. Caatinga was highly effective in terms of soil and water conservation at the small basin scale for both the dry and the wet season, resulting in a positive nexus between vegetation and water availability at the region.