Science-driven Integrated River Basin Management : a mirage?

The European Union Water Framework Directive (WFD) represents a new approach to the management of water across Europe. As part of the implementation of the WFD, integrated, catchment-scale plans for the protection and restoration of aquatic ecosystems must be developed. These plans need to be supported by new science, focused on understanding the general modes of behaviour of complex aquatic ecosystems, and the fundamental principles that govern this behaviour. This requires the collaborative production of new scientific knowledge, drawing on expertise from multiple academic disciplines, and refocusing on larger spatial and longer temporal scales. To mobilise existing scientific knowledge, and to produce new knowledge that is effectively adopted in policy and practice, scientists and managers must also develop collaborative partnerships involving the co-production and bidirectional exchange of knowledge. However, many personal and institutional barriers currently limit the development of such partnerships. Particular issues surround individual willingness to step outside disciplinary comfort zones, and the role of professional norms, rewards and value systems. The lack of training and support for individual knowledge-brokers, who work to develop these partnerships at the interface between science and management, is also a limiting factor. Even with such collaborative partnerships in place between scientists, and between scientists and managers, scientific knowledge will only ever be one contributor to the decision-making processes occurring within the WFD. Scientific knowledge will compete alongside issues of personal and institutional values, of moral judgements, of equity and of social justice in the consensus-building processes occurring within decision-making fora. The potential for, and the limits of, scientific knowledge to support the implementation of the WFD should be clearly recognised

Long-term effects of drinking-water treatment residuals on dissolved phosphorus export from vegetated buffer strips

The export of dissolved phosphorus (P) in surface runoff from agricultural land can lead to water quality degradation. Surface application of aluminium (Al)-based water treatment residuals (Al-WTRs) to vegetated buffer strip (VBS) soils can enhance P removal from surface runoff during single runoff events. However, the longer-term effects on P removal in VBSs following application of products such as Al-WTR remain uncertain. We used field experimental plots to examine the long-term effects of applying a freshly generated Al-WTR to VBSs on dissolved P export during multiple runoff events, occurring between 1 day and 42 weeks after the application of Al-WTR. Vegetated buffer strip plots amended with Al-WTR significantly reduced soluble reactive P and total dissolved P concentrations in surface runoff compared to both unamended VBS plots and control plots. However, the effectiveness of Al-WTR decreased over time, by approximately 70 % after 42 weeks compared to a day following Al-WTR application. Reduced performance did not appear to be due to drying of Al-WTR in the field. Instead, the development of preferential flow paths as well as burying of Al-WTR with freshly deposited sediments may explain these observations. Better understanding of the processes controlling long-term P removal by Al-WTR is required for effective management of VBSs

The hydraulic structure of a raised bog and its implications for ecohydrological modelling of bog development.

Raised bogs are important ecohydrological systems in which there are strong two-way links between plant succession, litter and peat decay, and hydrological functioning. Using recently established protocols, we measured the hydraulic structure of a raised bog in West Wales. We tested two hypotheses: (i) that the hydraulic conductivity (K) of the peat shows depth dependency such that lower layers of peat are effectively impermeable, and (ii) that the K of the marginal peat of the bog dome is lower than that in central areas. From 107 piezometer measurements we found there was depth dependency of K but that lower peat layers were not poorly permeable or impermeable. We also found that the K of the peat on the margin of the bog dome was generally significantly lower than that in central areas. Our results suggest that, for some bogs at least, it is important to simulate water flow through deeper peats when simulating peatland development or growth. They also raise the intriguing possibility that the low K of marginal peat is important in maintaining wet conditions in central bog areas, allowing bogs to reach greater thicknesses than they would do in the absence of the low-K margin; an idea first proposed for blanket bogs by Lapen et al. (2005)

The release of phosphorus to porewater and surface water from river riparian sediments.

Sediments can be both a source and a sink of dissolved phosphorus (P) in surface water and shallow groundwater. Using laboratory mesocosms, we studied the influence of flooding with deionized water and simulated river water on P release to solution using sediment columns taken from a riparian wetland. The mesocosm incubation results showed that rather than retaining nutrients, sediments in the riparian zone may be a significant source of P. Concentrations of dissolved P in porewater reached more than 3 mg L–1 and in surface water over 0.8 mg L–1 within a month of sediment inundation. The reductive dissolution of P-bearing iron (Fe) oxides was the likely mechanism responsible for P release. Dissolved P to Fe molar ratios in anaerobic samples were approximately 0.45 when columns were flooded with water that simulated the chemistry of the adjacent river. This suggests there was insufficient Fe in the anaerobic samples to precipitate all P if the solutions were oxygenated or transported to an aerobic environment. If the anaerobic wetland solutions were delivered to oxygenated rivers and streams adjacent to the riparian zone, the equilibrium concentration of P in these systems could rise. The timing of P release was inversely related to the nitrate (NO3–) concentration in floodwater. This indicates that in riparian zones receiving low nitrate loads, or where NO3– loads are being progressively reduced, the risk of dissolved P release may increase. These findings present particular challenges for restoration and management in riparian areas

Pollutant attenuation at the groundwater – surface water interface : A classification scheme and statistical analysis using national-scale nitrate data.

A classification scheme for pollutant natural attenuation potential at the groundwater–surface water interface is presented, and its predictive power for explaining baseflow river nitrate concentration investigated. Both the classification scheme and statistical analysis are undertaken at Water Framework Directive surface water body scale for England and Wales, in baseflow conditions when relative groundwater contribution to rivers is greatest. The results of multiple regression analyses demonstrate statistically significant relationships between the classification of natural attenuation potential, its component properties, and baseflow river nitrate concentration. Natural attenuation at the groundwater–surface water interface is shown to be a significant control on observed river nitrate concentrations, albeit less influential than land-use descriptors. The results indicate that natural attenuation processes have a measurable impact on baseflow river chemistry at surface water body scale, and that consideration of natural attenuation processes at the groundwater–surface water interface would improve regional and catchment-scale risk prediction, and could help in the design of more sustainable catchment management strategies