Modulation of the goodness of fit in hydrological modelling based on inner balance errors.

In hydrological modelling, a good result for the criterion of goodness of fit does not always imply that the hypothesis of mass conservation is fulfilled, and models can lose their essential physical soundness. We propose a way for detecting this anomaly by accounting the resulting water balance during model simulation and use it to modulate the obtained goodness of fit. We call this anomaly in water balance as "inner balance error of the model". To modulate the goodness of fit values, a penalty function that depends on this error is proposed. In addition, this penalty function is introduced into a multi-criteria objective function, which is also tested. This procedure was followed in modelling the Headwater of the Tagus River (Spain), applying the monthly abcd water balance model. Modulation of the goodness of fit allowed for detecting balance errors in the modelling, revealing that in the simulation of some catchments the model tends to accumulate water in, or release water from, the reservoir that simulates groundwater storage. Although the proposed multi-criteria objective function solves the inner balance error for most catchments, in some cases the error cannot be corrected, indicating that any error in the input and output data is probably related to groundwater flows.

Appraisal of the water footprint of irrigated agriculture in a semi-arid area: The Segura River Basin.

Irrigated agriculture is a key activity in water resources management at the river basin level in arid and semi-arid areas, since this sector consumes the largest part of the water resources overall. The current study proposes a methodology to evaluate the water footprint (WF) of the irrigated agriculture sector at the river basin level, through a simulation of the anthropised water cycle combining a hydrological model and a decision support system. The main difference from the approaches that have already been used is that the new methodology includes the limitations of the system for the exploitation of water resources where the irrigated areas are located, and it considers the hydrological principles governed by the law of continuity of mass. Water footprint accounting was carried out for the Segura River Basin (South-eastern Spain), applying the methodology proposed and another that is usually applied. The results of the two methodologies were compared, revealing significant differences in the values of the WF, basically due to the blue component. The methodology that is usually applied overestimated the WF of the agriculture in the basin since supply deficits were not taken into account, providing results that would only be possible if there were no spatial or temporal restrictions to water use. So, in order to make the WF indicator useful in water resources management plans, it is necessary to adapt the computations to the main characteristics of the water exploitation system of the whole basin under study, respecting the hydrological principles of the water cycle: regulation and transport infrastructure, the real water resources available and the priority of access to water between concurrent water uses.

Pharmaceutical grey water footprint: Accounting, influence of wastewater treatment plants and implications of the reuse.

Emerging pollutants, including pharmaceutical compounds, are producing water pollution problems around the world. Some pharmaceutical pollutants, which mainly reach ecosystems within wastewater discharges, are persistent in the water cycle and can also reach the food chain. This work addresses this issue, accounting the grey component of the water footprint (GWFP) for four of the most common pharmaceutical compounds (carbamazepine (CBZ), diclofenac (DCF), ketoprofen (KTP) and naproxen (NPX)). In addition, the GWFC for the main conventional pollutants is also accounted (nitrate, phosphates and organic matter). The case study is the Murcia Region of southeastern Spain, where wastewater treatment plants (WWTPs) purify 99.1% of the wastewater discharges and there is an important direct reuse of the treated wastewater in irrigation. Thus, the influence of WWTPs and reuse on the GWF is analysed. The results reveal that GWFP, only taking into account pharmaceutical pollutants, has a value of 301 m3 inhabitant-1 year-1; considering only conventional pollutants (GWFC), this value increases to 4718 m3 inhabitant-1 year-1. So, the difference between these values is such that in other areas with consumption habits similar to those of the Murcia Region, and without wastewater purification, conventional pollutants may well establish the value of the GWF. On average, the WWTPs reduce the GWFC by 90% and the GWFP by 26%. These different reductions of the pollutant concentrations in the treated effluents show that the GWF is not only due to conventional pollutants, and other contaminants can became critical, such as the pharmaceutical pollutants. The reuse further reduces the value of the GWF for the Murcia Region, by around 43.6%. However, the reuse of treated wastewater is controversial, considering the pharmaceutical contaminants and their possible consequences in the food chain. In these cases, the GWF of pharmaceutical pollutants can be used to provide a first approximation of the dilution that should be applied to the treated wastewater discharges when they are reused for another economic activity that imposes quality restrictions. For the case of agriculture in the Murcia Region, the dilution required is 2 (fresh water) to 1 (treated wastewater), taking into account the pollution thresholds established in this work.

Probabilistic evaluation of the water footprint of a river basin: Accounting method and case study in the Segura River Basin, Spain.

In the current study a method for the probabilistic accounting of the water footprint (WF) at the river basin level has been proposed and developed. It is based upon the simulation of the anthropised water cycle and combines a hydrological model and a decision support system. The methodology was carried out in the Segura River Basin (SRB) in South-eastern Spain, and four historical scenarios were evaluated (1998-2010-2015-2027). The results indicate that the WF of the river basin reached 5581 Mm3/year on average in the base scenario, with a high variability. The green component (3231 Mm3/year), mainly generated by rainfed crops (62%), was responsible for the great variability of the WF. The blue WF (1201 Mm3/year) was broken down into surface water (56%), renewable groundwater (20%) and non-renewable groundwater (24%), and it showed the generalized overexploitation of aquifers. Regarding the grey component (1150 Mm3/year), the study reveals that wastewater, especially phosphates (90%), was the main culprit producing water pollution in surface water bodies. The temporal evolution of the four scenarios highlighted the successfulness of the water treatment plans developed in the river basin, with a sharp decrease in the grey WF, as well as the stability of the WF and its three components in the future. So, the accounting of the three components of the WF in a basin was integrated into the management of water resources, it being possible to predict their evolution, their spatial characterisation and even their assessment in probabilistic terms. Then, the WF was incorporated into the set of indicators that usually is used in water resources management and hydrological planning.

The Water Footprint as an indicator of environmental sustainability in water use at the river basin level.

One of the main challenges in water management is to determine how the current water use can condition its availability to future generations and hence its sustainability. This study proposes the use of the Water Footprint (WF) indicator to assess the environmental sustainability in water resources management at the river basin level. The current study presents the methodology developed and applies it to a case study. The WF is a relatively new indicator that measures the total volume of freshwater that is used as a production factor. Its application is ever growing in the evaluation of water use in production processes. The calculation of the WF involves water resources (blue), precipitation stored in the soil (green) and pollution (grey). It provides a comprehensive assessment of the environmental sustainability of water use in a river basin. The methodology is based upon the simulation of the anthropised water cycle, which is conducted by combining a hydrological model and a decision support system. The methodology allows the assessment of the environmental sustainability of water management at different levels, and/or ex-ante analysis of how the decisions made in water planning process affect sustainability. The sustainability study was carried out in the Segura River Basin (SRB) in South-eastern Spain. The SRB is among the most complex basins in Europe, given its special peculiarities: competition for the use, overexploitation of aquifers, pollution, alternative sources, among others. The results indicate that blue water use is not sustainable due to the generalised overexploitation of aquifers. They also reveal that surface water pollution, which is not sustainable, is mainly caused by phosphate concentrations. The assessment of future scenarios reveals that these problems will worsen if no additional measures are implemented, and therefore the water management in the SRB is environmentally unsustainable in both the short- and medium-term.