Ensuring a sufficient and adequate supply of water for humans and ecosystems is a pressing environmental challenge. The expansion of agricultural and urban lands has jeopardized watershed ecosystem services and a changing climate poses additional risks for regional water supply. We used stream water quality data collected between 2000 and 2014, coupled with detailed precipitation and land cover information, to investigate the effects of landscape composition and short-term precipitation variability on the quality of water resources in the state of São Paulo, Brazil. The state is home to over 45 million people and has a long history of human landscape modification. A severe drought in 2014–2015 led to a major water crisis and highlighted the fragility of the regional water supply system. We found that human-dominated watersheds had lower overall water quality when compared to forested watersheds, with urban cover showing the most detrimental impacts on water quality. Forest cover was associated with a better overall water quality across the studied watersheds, with forested watersheds having low turbidity and high dissolved oxygen. High precipitation led to increased turbidity and fecal coliforms levels and lower dissolved oxygen in streams but these effects depended on watershed land cover. High precipitation diluted concentrations of nitrogen and dissolved solids in highly urbanized watersheds but exacerbated turbidity in pasture-dominated watersheds. Given the high costs of water treatment in densely populated regions, there is a pressing need to plan and manage landscapes in order to ensure adequate water resources. In tropical regions, maintaining or restoring native vegetation cover is a promising intervention to sustain adequate water quality.

中文翻译：

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在不断变化的气候下，原生森林覆盖保护溪流水质

确保为人类和生态系统提供充足和充足的水供应是一项紧迫的环境挑战。农业和城市用地的扩张危及流域生态系统服务，气候变化给区域供水带来了额外风险。我们使用 2000 年至 2014 年收集的溪流水质数据以及详细的降水和土地覆盖信息，研究了巴西圣保罗州的景观组成和短期降水变化对水资源质量的影响。该州拥有超过 4500 万人口，拥有悠久的人文景观改造历史。2014-2015 年的严重干旱导致了严重的水危机，凸显了区域供水系统的脆弱性。我们发现，与森林覆盖的流域相比，人类主导的流域的整体水质较低，城市覆盖对水质的不利影响最大。森林覆盖与整个研究流域更好的整体水质有关，森林流域具有低浊度和高溶解氧。高降水导致浊度和粪便大肠菌群水平增加以及溪流中溶解氧降低，但这些影响取决于流域土地覆盖。在高度城市化的流域中，高降水稀释了氮和溶解固体的浓度，但加剧了以牧场为主的流域的浊度。鉴于人口稠密地区的水处理成本高昂，迫切需要规划和管理景观以确保充足的水资源。