Surface water quality of the Middle San Francisco river basin after the implementation of irrigated perimeters of Gorutuba/Lagoa Grande and Jaíba

ABSTRACT The irrigation perimeters of Jaíba and Gorutuba/Lagoa Grande are located in the Minas Gerais portion of the Middle São Francisco river basin, Brazil, occupying an area of approximately 31,493 ha. This region has the potential to contaminate water resources as a result of urbanization, deforestation and the application of fertilizers and pesticides in agricultural activities. The aim of this research was to investigate the impact of irrigation on surface water quality in the region, using secondary monitoring. Nine monitoring stations were selected in the region, which represent the diferente uses and occupation of land. The cluster analysis and the nonparametric Kruskal-Wallis test, followed by multiple comparisons, were used to comparatively evaluate the sampling stations and to identify which parameters showed different behavior among these stations. Although it was not possible to observe a pattern of contamination due to the location of the stations, it was found that the stations located along the São Francisco river showed no significant differences, although the use and occupation of land were different. The temporal trend of the constituents was verified by applying the test of the hypothesis of stationarity Spearmant, which found that most of the data analyzed were not stationary, with a tendency of increase or decrease over the analysis period. After the application of these statistical tests, it was concluded that, in general, the implementation of irrigated perimeters caused low impact in water quality in the region, in the period studied, considering the parameters analyzed in this study.

摘要 巴西圣弗朗西斯科河中游流域的米纳斯吉拉斯州（Minas Gerais）境内分布有雅伊巴（Jaíba）与戈鲁图巴/拉戈阿格兰德（Gorutuba/Lagoa Grande）两处灌溉区，总面积约31493公顷。该区域因城市化进程、森林砍伐以及农业活动中化肥与农药的施用，存在污染水资源的潜在风险。本研究依托二手监测数据，旨在探究该区域灌溉活动对地表水水质的影响。研究区内共选取9个监测站点，以覆盖不同的土地利用与土地覆被类型。研究采用聚类分析、非参数克鲁斯卡尔-沃利斯检验（Kruskal-Wallis test）结合多重比较法，对采样站点开展对比评估，并识别出在各站点间表现存在显著差异的监测参数。尽管未能依据站点位置观测到明确的污染分布模式，但研究发现沿圣弗朗西斯科河布设的监测站点之间并无显著差异，即便其土地利用与覆被情况各不相同。本研究通过斯皮尔曼（Spearman）平稳性假设检验验证了各组分的时间趋势，结果显示绝大多数分析数据并非平稳序列，在研究周期内呈现出上升或下降的变化趋势。经上述统计检验分析后可得出结论：在本研究所涵盖的分析参数范围内，在所研究时段内，灌溉区的建设对该区域水质的整体影响较低。