Designing river water quality policy interventions with scarce data: the case of the Middle Tagus Basin, Spain

Abstract

Anthropic pressure deteriorates river water quality, so authorities need to identify the causes and define corrective action. Physically based water quality models are a useful tool for addressing physico-chemical pollutants, but they must be calibrated with an amount of data that is often unavailable. In this study we explore the characterization of a model to design corrective intervention in the context of sparse data. A calibration indicator that is both A c c e p t e d M a n u s c r i p t 2 simple and flexible is proposed. This approach is applied to the Middle Tagus Basin in central Spain, where the physico-chemical concentration of pollutants is above legal standards. We quantify the effects of the main existing pressures (discharge from wastewater treatment plants, agricultural diffuse pollution and a major inter-basin water transfer) on the receiving waters. In particular, the study finds that wastewater treatment plant effluent concentrations should be reduced to up to 0.65 mg/L of ammonium and 0.55 mg/L of phosphate to achieve the environmental goals. We propose and prioritize a set of policy actions that would contribute to the good status of surface water bodies in the region.

Integrated Surface-Groundwater Modelling of Nitrate Concentration in Mediterranean Rivers, the Júcar River Basin District, Spain

“…Additionally, it has been used to evaluate climate change impacts on water resources [32], to improve the drought's indicators in the Júcar RBD [33], and to observe changes in the hydrology in the Mediterranean side of Spain [27]. In previous works, RREA was used to quantify the effects of the main existing pressures on the receiving waters in the Middle Tagus Basin in Spain [34]. Among the multiple benefits of these models, they can be used to identify pollution sources, simulate nitrate concentration in surface and groundwater, and assess the efficiency of management measures to prevent water degradation.…”

Multi-objective optimal design of interbasin water transfers: The Tagus-Segura aqueduct (Spain)

“…However, the estimation of surplus resources in the donor basin has been long questioned, arguing that the environmental effects have been not rigorously taken into account (Hernández-Mora et al, 2014;Rey et al, 2016). According to WWF (2009), the reduced stream flows have affected riparian vegetation along the Tagus River and have limited the river capacity to dilute the polluted flows produced by the Madrid region, resulting in water quality problems between Aranjuez and Toledo (Bolinches et al, 2020;Hernández-Mora and del Moral, 2015).…”

Analysis of the Evolution of Climatic and Hydrological Variables in the Tagus River Basin, Spain

“…The urban areas of Madrid and Toledo are located in the middle part of the basin (see Figure 1) and host 5.1 and 0.6 million inhabitants, respectively. The water demand of the capital city-about 500 Hm 3 •year −1 -is met mainly from reservoirs in the Lozoya river [33] (see location in Figure 1) and is returned mostly to the Manzanares river, which is under pressure from the domestic pollution load [34,35].…”