Hydrological modeling of the Ribeirão das Posses - An assessment based on the Agricultural Ecosystem Services (AgES) watershed model

Abstract Southeastern Brazil has recently experienced drought conditions that have impacted watershed conservation and the management of water quality and quantity for agricultural and urban demands. The Ribeirão das Posses watershed is being monitored as a headwater of the Jaguarí River, which is one of the contributing rivers of the Cantareira Reservoir Complex in the state of São Paulo. The landscape has changed over the last century from native forests to more homogeneous vegetation for pastures, crops and some forest plantations of eucalyptus, which have cumulative impacts on water yield and quality. Currently, the Projeto Conservador das Águas (Water Conservationist Project) has planted small areas with native species vegetation in order to recover degraded areas. The objective of this study was to evaluate the quantity of water in the Ribeirão das Posses Basin by both measurements and by simulating hydrological responses. The Agricultural Ecosystem Services (AgES) watershed model was applied to simulate water movement and storage among land areas. The simulation period was from 2009 to 2014, because the daily streamflow and meteorological data were available for model calibration and testing. We discuss data input requirements, model calibration to fit measured streamflow, and sensitivity to spatially variable rainfall inputs. The calibrated model may be used to estimate streamflow during periods of missing data, and in the future to estimate impacts of land use changes on stream water quantity and quality. Such information can be used in programs of payments for ecosystem services.

摘要：巴西东南部近期遭遇干旱灾害，对流域保护以及农业、城市用水需求下的水质与水量管理均造成了显著影响。波萨斯溪（Ribeirão das Posses）流域作为雅瓜里河（Jaguarí River）的源头流域被纳入监测体系，而雅瓜里河是圣保罗州坎塔雷拉水库群（Cantareira Reservoir Complex）的补给河流之一。近一个世纪以来，该区域景观已从原生森林转变为以牧场、农作物及部分桉树人工林为主的同质化植被，这对流域产水量与水质产生了累积性影响。当前，水源保护项目（Projeto Conservador das Águas）已在小范围区域种植本土植被，以修复退化地块。本研究旨在通过实地测量与水文响应模拟两种手段，评估波萨斯溪流域的水量状况。研究采用农业生态系统服务（Agricultural Ecosystem Services, AgES）流域模型，模拟陆域范围内的水分运移与存储过程。模拟时段设定为2009年至2014年，因该时段具备可用于模型率定与验证的日径流及气象数据。本研究探讨了模型的数据输入要求、适配实测径流的模型率定方法，以及对空间异质性降雨输入的敏感性。经率定后的模型可用于估算数据缺失时段的径流量，未来还可用于评估土地利用变化对河流水质与水量的影响。此类研究结果可应用于生态系统服务付费项目中。