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Mitigation Of Low Flows In An Agricultural Catchment In Eastern Scotland: Can A Combined Ecological And Economic Case Be Made For Investment In Smart Regulation Of Water Flows?

Congress: 2015
Author(s): Andrew Vinten, Lindsay Rear , James Sample, Paula Novo, Marshall Halliday
James Hutton Institute1, McGill University2, Esk Rivers and Fisheries Trust3

Keyword(s): Sub-theme 9: Water allocation among competing uses and users,
AbstractANDY VINTEN1,JAMES SAMPLE1, LINDSAY REAR2, PAULA NOVO1, MARSHALL HALLIDAY3. 1JAMES HUTTON INSTITUTE, ABERDEEN AB15 8QH, UK. TEL: 0044 1224 395165. EMAIL: ANDY.VINTEN@HUTTON.AC.UK; 2MCGILL UNIVERSITY, QUEBEC, CANADA; 3ESK RIVERS AND FISHERIES TRUST, ANGUS, UK. Introduction. Catchment scale assessment of demands for water services, such as wetland and river ecology, irrigation requirements, flood risk mitigation and water quality can lead to robust and innovative approaches to delivery of improved ecosystem services. Several of these water demands are present in the Lunan water, an agricultural catchment in Eastern Scotland. We have explored the case for actively managing flows from upstream wetlands of high conservation value as a means of increasing water benefits across a range of stakeholders. First we assessed the risk of irrigation abstraction causing failure in low flows standards for good ecological status required by the WFD. This assessment was used to establish whether improved management of releases from upstream wetlands could be achieved with non-detrimental or positive effects on the wetlands, while providing significant improvement in water services downstream. Such an analysis could facilitate local adaptation of the existing abstraction licencing scheme, to deliver both novel technical and governance solutions based on a participatory process with a well established stakeholder group. Methods/Materials. The Lunan catchment is a mixed arable farmland catchment that drains an area of 134 km2 from its source near Forfar to the North Sea at Lunan Bay, underlain by groundwater bodies in Old Red Sandstone. For the analysis of potential for improved water management, we made use of the following datasets: (1) a 20 year dataset for Lunan Water discharge at Kirkton Mill, near the mouth of the river (from Scottish Environment Protection Agency); (2) a dataset of licenced maximum and actual abstraction for 2011-2013 (from the Public Registry);( (3) a 12 year dataset of water levels in Balgavies Loch and the associated wetland at Fonah Bog (courtesy of A. Houghton, Scottish Wildlife Trust), which retain water in the upper catchment; 4) a 10 year bio-economic modelling study of impacts of flow restriction on potato irrigation, yields and gross margins in two catchments in Eastern Scotland (Crabtree et al., 2002). We identified regulatory standards for low flows and advisory guidelines (<10cm standing water) for management of wetlands (Wheeler et al., 2004). We held two local stakeholder meetings in 2014 to discuss water management issues (Rear et al., 2014) and inform our approach. Results and Discussion. The low flow regulatory standard for good ecological status is that <10% of long term Q95 should be abstracted when daily flows are < Q95 (0.195 m3/s). The regulator's risk assessment of environmental impact is currently based on licensed maxima (totalling 55% of Q95) leading to clear downgrading of ecological status. The regulator aspires to use actual data if more accurate returns were made. This would allow improved security of water supply, identification of minimum mitigation measures to improve downgrading, and dialogue with licenceholders about limits that more accurately reflect activity. For two of the three years since returns have been mandatory, the actual water abstraction returns were very low (19,691 m3 in 2011 and zero in 2012). In 2013, a dry year, the recorded abstraction was 204,252 m3/year, or 19,404m3 in excess of water use that would be compliant with regulation. This was probably an underestimate, as only 23 out of 73 licence locations gave positive water use returns. Whereas river discharge showed no significant long term trends (Dunn et al., 2014), measured water levels in Balgavies Loch showed significant upward trends in maximum (r2 = 0.80, slope = 3.7cm per year) and minimum (r2 =0.39, slope = 0.7cm per year) annual water levels. Even in the second half of the summer, Fonah bog would benefit from lower levels (<10cm standing water) over 40% of the time. Crabtree et al (2002) evaluated the economic impact of irrigation abstraction controls associated with low flows for two rivers in Eastern Scotland, using net-back analysis and bio-economic modelling. Over ten years, average annual losses in gross margin, where irrigation restrictions were in place at Q90, were £609k and £276k for the two rivers. Decrease in water use was 86,100 and 81,100 m3 respectively. These give marginal costs of restricted water use at low flows of £7.1 and £3.4/m3 respectively. Using the mean figure of £5.2/m3, the economic value of the additional water availability associated with flow release for irrigation from the wetlands, while achieving compliance with ecological standards downstream, was ca.£100k for 2013.This could readily offset annualised infrastructure and transaction costs, for example associated with installation of a programmable tilting weir at the outlet to the lochs (see Rickard, Day and Purseglove, 2003. Conclusion. An economic and ecological case for level water management in upstream wetlands has been scoped for the Lunan Water. This is based on the likely upgrade in ecological status of river and wetlands, increased availability of water for irrigation, and potential benefits of flood risk mitigation. Novel ecologically friendly hydraulic structures could help facilitate this adaptation. The challenge for local stakeholders of achieving a viable approach to governance remains. References. 1. Crabtree, J. R., Dunn S., Chalmers, N. and Stalham, M. (2002). Evaluating the Economic Impact of Irrigation Controls. Report to SEERAD. Macaulay Land Use Research Institute, Aberdeen. Published by SEERAD at 2. Dunn, S. M., Sample, J., Potts, J., Abel, C., Cook, Y., Taylor, C., & Vinten, A. J. A. (2014). Recent trends in water quality in an agricultural catchment in Eastern Scotland: elucidating the roles of hydrology and land use. Environmental Science: Processes & Impacts. doi:10.1039/c3em00698k 3. Rickard,C. Day,R. and Purseglove,J. (2003). River Weirs – Good Practice Guide.section A, p5. R&D Publication W5B-023/HQP, Environment Agency. 4. Wheeler, B.D. Gowing,D.J.G., Shaw, S.C., Mountford, J.O. and Money, R.P. (2004). Ecohydrological Guidelines for Lowland Wetland Plant Communities Final Report Environment Agency - Anglian Region Edited by A.W. Brooks, P.V. José, and M.I. 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2011 IWRA - International Water Resources Association - - Admin