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Accounting For The Grey Water Footprint In Three Freshwater Sites In Scotland: Nurture Or Nature?

Congress: 2015
Author(s): Paula Novo, Alejandro Sereno, Antonio Alvarez-Valero
The James Hutton Institute. Social, Economic and Geographical Sciences Group1, Dept. Geology, Universidad de Salamanca, Spain2

Keyword(s): Sub-theme 10: Management of water resources,
Abstract1. Introduction There is an increasing interest in accounting for both the contribution of water resources to the economy and the impact the economy has on water systems (Russi and ten Brink, 2013). Considerable experience exists with water quantity accounts in national accounting systems, as reflected in the System for Environmental Economic Accounts Central Framework (SEEA, CF), which is the standardised system for environmental accounting (United Nations, 2012). However, less experience exists regarding the inclusion of water quality issues in standardised environmental-economic accounts. So far, water quality accounts are still experimental in the SEEA- Water and describe only the total change in quality for the accounting period. The water footprint has been increasingly used for understanding the impact of production and consumption patterns on water resources (Hoekstra et al., 2011). In addition, the grey water footprint (GWF) has been developed to take into account water quality issues as the volume needed to assimilate a pollutant load on a water body (Franke et al., 2013). The geological features of a particular site strongly influence the content of chemical elements released into freshwater bodies and, therefore, the assessment of the GWF in areas without anthropogenic intervention can be used as a key indicator of potential environmental changes that naturally occur in pristine sites. This study builds on the water footprint method and uses the GWF as an indicator to understand the links between geology and water quality in three freshwater sites in Scotland. For this purpose, we use information on water quality parameters form the Environmental Change Network (ECN) database, and incorporate them into a grey water footprint assessment. 2. Materials and Methods The ECN database comprises 45 freshwater and 12 terrestrial sites distributed across the UK. This research focuses in 3 freshwater sites: Lochnagar (L09), Loch Kinord (L14) and Spey at Fochabers (R15). The studied database covers the period 2000-2012. ECN freshwater chemistry information consists on a collection of samples from standing and running waters (or automatic recording where appropriate) that measures physical variables of aquatic environmental importance. The selected variables in this research show changes in freshwater sites as well as biogeochemical or biological activity in the environmental system. The GWF denotes the water volume required to dilute pollutants or any chemical substances to such an extent that the quality of the water remains above agreed ambient water quality standards (Franke et al., 2013; Hoekstra et al., 2011).In this study the GWF is presented as a ratio between the pollutant load and the capacity of the water system to assimilate this pollution, once established a particular standard, multiplied by the run-off of the water body. The quality parameters for different elements and substances in the water are defined in the Directive 98/83/EC, amended by Regulation (EC) NÂș 596/2009 of the European Parliament and in the Guidelines for the quality of drinking water by the World Health Organization (WHO). If the ratio between the pollutant concentration and the capacity of the water system to assimilate this pollutant is 1 the system is operating at the limit in which the capacity to deal with pollution is the same as the pollution level. If the ratio is >1 the pollution level is higher than the capacity, thus yielding to a system under stress. When the ratio is <1 the pollution is below the assimilation capacity. 3. Results and discussion In this section, we present GWF values for the Spey site, for which data on discharge are available, and results on the assimilation capacity of the water system for the three freshwater sites considered in the study (Note: figures available, but not included in this abstract as the online platform doesn't upload them). The GWF includes estimates for the nutrients ammonium, nitrate, nitrite and phosphate, as well as the elements and metals aluminium, arsenic, cadmium, carbon chloride, copper, iron, manganese, mercury, nickel, lead, sodium, sulphur and zinc. The overall GWF represents the mean values during the 13 years. On an average basis for the period 2000-2009, the highest GWF corresponds to ammonium (1.427 m3/s), whereas the lowest GWF is for phosphate (0.202 m3/s). However, the highest GFW value for nutrients during 2000-2009 corresponds to nitrite, (24.083 m3/s). The highest value of GWF in metals corresponds to iron (10981.858 m3/s). As expected, the GWF for elements in dissolved form is lower than the GWF for total metals. Total iron shows the highest GWF average for the period 2000-2012 (129450 m3/s), followed by aluminium (93041 m3/s). Lower values correspond to copper in both forms (dissolved and total: 0.013 and 0052 m3/s) and cadmium in dissolved form (0.033 m3/s). The GWF ratios for nutrients are in all cases lower than 1. Therefore, the system seems able to cope with the nutrient levels. For aluminium, manganese and iron the GWF ratios are significantly higher than 1. The variation of the GWF ratio for these elements is very similar in the three freshwater sites. The geochemical results and their relationships to the physical variables of the studied areas provide interesting insights. Concerning the metal concentrations, Lochnagar, Loch Kinord and Spey at Fochabers evidence a clear trend that match their concentration peaks in water with the peaks of surface water discharge that, in turn, match with periods of high rainfalls. The pH values remain fairly constant, not depending on significant variations in element concentrations which highly regulate the acidity of the water. The absence of a particular relationship might be due to the presence of environmental minerals that control the dissolution-precipitation of these elements. 4. Conclusions This study highlights the relevance of considering multiple sources of pollution in the water and the links among them. Thus, in the case of Lochnagar, it is clear that the geochemical and atmospheric conditions determine the ultimate capacity of the system to deal with pollution. In addition, the fairly constant pH values below 6 at Lochnagar, and around 7 at Loch Kinord and Spey at Fochabers, as well as the likely presence of particular environmental-minerals, control the dissolution-precipitation of these elements and therefore their subsequent potential pollution. In addition, the study suggests that there is a direct relationship among the peak values of GWF, leaching runoff fraction for nutrients and metals, surface water discharge, and rainfall. The overall GWF represents the peak estimate of the average values during the 13 years, concluding that ammonium shows the highest value. However, the highest GWF value for nutrients corresponds to nitrite, implying that considering only average values for a period in the GWF might disregard the relevance 1. Franke N.A., Boyacioglu H., Hoekstra A.Y., 2013. Grey Water Footprint Accounting: Tier 1 Supporting Guidelines. UNESCO-IHE Institute for Water Education. The Netherlands, 64. 2. Hoekstra, A.Y., Chapagain, A.K., Aldaya, M.M., Mekonnen, M.M., 2011. The water footprint assessment manual: setting the global standard. Earthscan: London. 3. Russi D., ten Brink P., 2013. Natural Capital Accounting and Water Quality: Commitments, Benefits, Needs and Progress. A Briefing Note. The Economics of Ecosystems and Biodiversity (TEEB), 20. 4. United Nations, 2012. System of Environmental-Economic Accounting Central Framework. White cover publication, pre-edited text subject to official editing, UNSD, New York.
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