Enhancing LULC scenarios impact assessment in hydrological dynamics using participatory mapping protocols in semiarid regions.

Land use and land cover (LULC) scenarios in rural catchment hydrology are crucial to describe the effects of future water dynamics. However, there is a lack of understanding of the effectiveness of including static land covers at the subbasin level to provide inter-annual stability in changing the different water balance components. We developed a step-by-step mapping protocol to extend and enrich the hydrological assessment of future LULC scenarios defined through participatory stakeholder involvement. This novelty included specific allocation of static and dynamic LULC change among the scenarios and then compared the change of water dynamics to the current situation. For this, we quantified the LULC impact on the components of the water balance from three contrasting participatory scenarios implemented with the SWAT model in a rural basin in central Spain. The Land-sharing scenario (LSH) had the highest percentage of permanent grassland and shrubs and no increase of irrigated land compared to baseline. The land-sparing scenario (LSP) intensified agricultural land use close to urban areas, and the land balance scenario (LBA) was intermediate. The LSH increased the aquifer recharge by +1.7% and streamflow by +1.5%, while evapotranspiration and soil water storage decreased by -0.2%. In contrast, the LBA decreased in the riverine flux of -0.5%, an aquifer recharge of -0.6%, a soil water storage of -3.5%, and an evapotranspiration rate of +0.3%. Thus, LSH revealed that the allocation of permanent land cover such as grassland could buffer water dynamics, suggesting that dedicated planning and allocation of permanently vegetated LULC will favour land and water conservation.

Identification of contaminants of concern in the upper Tagus river basin (central Spain). Part 2: Spatio-temporal analysis and ecological risk assessment.

This study provides a description of the water quality status in the tributaries of the upper Tagus River and a preliminary risk assessment for freshwater organisms. A wide range of physico-chemical parameters, nutrients, metals and organic contaminants (20 pesticides, and 32 point source chemicals, mainly pharmaceuticals) were monitored during spring, summer and autumn of 2016. Monitoring of organic contaminants was performed using conventional grab sampling and passive samples (POCIS). The variation of the different groups of parameters as regards to land use and sampling season was investigated. The prioritization of organic and inorganic contaminants was based on the toxic unit (TU) approach, using toxicity data for algae, invertebrates and fish. Finally, the compliance with the Environmental Quality Standards (EQS) set as part of the Water Framework Directive (WFD) was evaluated for the listed substances. This study shows that the land use characteristics had a large influence on the spatial distribution of the contaminants and other water quality parameters, while temporal trends were only significant for physico-chemical parameters, and marginally significant for insecticides. Acute toxicity is likely to occur for some metals (copper and zinc) in the most impacted sites (TU values close to or above 1). Low acute toxicity was determined for organic contaminants (individual compounds and mixtures) on the basis of grab samples. However, the assessment performed with POCIS samples identified diuron, chlorpyrifos and imidacloprid as potentially hazardous compounds. Several contaminant mixtures that may cause chronic toxicity and that should be considered in future regional chemical monitoring plans were identified. Our study also shows that some metals and pesticides exceeded the WFD regulatory thresholds and that only 30% of the sampled sites had a good chemical status. Further research is needed to identify chemical emission sources and to design proper abatement options in the Tagus river basin.