Semi-arid regions are known for erratic precipitation patterns with significant effects on the hydrological cycle and water resources availability. High temporal and spatial variation in precipitation causes large variability in runoff over short durations. Due to low soil water storage capacity, base flow is often missing and rivers fall dry for long periods. Because of its climatic characteristics, the semi-arid north-eastern region of Brazil is prone to droughts. To counter these, reservoirs were built to ensure water supply during dry months. This paper describes problems and solutions when calibrating and validating the eco-hydrological model SWIM for semi-arid regions on the example of the Pajeú watershed in north-eastern Brazil. The model was calibrated to river discharge data before the year 1983, with no or little effects of water management, applying a simple and an enhanced approach. Uncertainties result mainly from the meteorological data and observed river discharges. After model calibration water management was included in the simulations. Observed and simulated reservoir volumes and river discharges are compared. The calibrated and validated models were used to simulate the impacts of climate change on hydrological processes and water resources management using data of two representative concentration pathways (RCP) and five earth system models (ESM). The differences in changes in natural and managed mean discharges are negligible (< 5%) under RCP8.5 but notable (> 5%) under RCP2.6 for the ESM ensemble mean. In semi-arid catchments, the enhanced approach should be preferred, because in addition to discharge, a second variable, here evapotranspiration, is considered for model validation.

中文翻译：

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模型校准对气候变化下半干旱流域水文和水资源管理模拟的影响

半干旱地区以不稳定的降水模式而闻名，对水文循环和水资源的可用性有显着影响。降水的高时空变化会导致径流在短时间内发生很大变化。由于土壤蓄水能力低，基流经常缺失，河流长期干涸。由于气候特点，巴西东北部半干旱地区容易发生干旱。为了解决这些问题，建造了水库以确保干旱月份的供水。本文以巴西东北部的 Pajeú 流域为例，描述了在校准和验证半干旱地区生态水文模型 SWIM 时的问题和解决方案。该模型根据 1983 年之前的河流流量数据进行校准，水管理没有或几乎没有影响，采用简单和增强的方法。不确定性主要来自气象数据和观察到的河流流量。模型校准后，水管理被包括在模拟中。观察和模拟的水库体积和河流流量进行了比较。校准和验证的模型用于使用两个代表性浓度路径 (RCP) 和五个地球系统模型 (ESM) 的数据模拟气候变化对水文过程和水资源管理的影响。对于 ESM 集合平均值，在 RCP8.5 下，自然和管理平均流量变化的差异可以忽略不计（< 5%），但在 RCP2.6 下则显着（> 5%）。在半干旱集水区，应首选强化方法，因为除了流量外，还有第二个变量，