Assessing sustainable water use and local economy in Korea

With increasing concern about limited water resources, many countries and international organizations have launched a framework to assess water sustainability in domestic and global scopes (Esty et al., 2005 for ESI; Hsu et al., 2013 for EPI). The purpose of this study was to develop a Sustainable Water Index (SWI)to estimate water use sustainability and to explorethe relationship between SWI and local economy in Korea.As previously conducted study verifying water indicators between global and country-level dataset, we employed that a global assessment on water security (Vörösmarty et al., 2010) showed acceptable level of spatial distribution in their threat indicators while poor performance in delineating responsive indicators (Kim et al., 2014) in country-level. In the universal terms of sustainability and upcoming consequences due to climate change, raising alleviation capacity (Response)is getting more crucial to mitigate the current threats (Pressure). Therefore, methodical assessment and verification on water sustainability are essentially required to diagnose the local issues and grasp the possible solutions using domestic data and thorough analysis.

Before defining a framework inclusively to assess water sustainability in Korea, we carefully reviewed a wide-range of literature to build up a comprehensive framework with relevant and essential indicators. As a result, we applied a set of 23 indicators incorporated with the four themes (availability, use, pollution, and management capacity) and P-Rsystem partly adopted from OECD (Nardoo et al., 2005). Four themes in the framework were comprised of major environments in using water and P-R system was adopted to consider the drivers and their counterbalances in terms of pressure and response.

Theme / Pressure / Response
Sub-theme / Indicator / Sub-theme / Indicator
Water availability / Climate (discharge) / Monthly variability / Water storage / Effective water storage
Inter-annual variability / Alternative water resources / Water reuse, rainwater harvesting
groundwater / Groundwater level change
Water use / Consumption / Water consumption / Water access / Water supplycoverage
Demand / Human water stress
Intensity / Water use intensity
Water pollution / Sanitation / Sanitation / Sanitation / Sanitation coverage
Wastewater / Wastewater
Sediment / Sediment loading / Wastewater / Sewerage coverage
Water quality / BOD
Phosphorus loading
Management Capacity / Watershed environment / Impervious areas / Watershed environment / Environmental areas
Finance / Water supply price / Financial investment / Investment on water supply
Sewerage service price
Efficiency / Water leakage / Investment on sewerage

Table 1 Framework for Sustainable Water Index

Each indicator was calculated after reviewing applicable methodologies and available datasets respectively and then normalized using cumulative distribution function (CDF) to distribute raw data in standardized manner from 0 to 1. Then indicators under each theme were aggregated using equal weights and four thematic indices were averaged to calculate Pressure and Response index respectively. In calculating SWI, “1-(Pressure index * (1- Response index))” was adoptedfrom Vörösmarty et al (2010) in a modified form. As a result, we estimated SWI for 109 of watersheds and additionally focused on 6major cities in Korea for a year of 2010. Furthermore, local economic status was evaluated using gross regional domestic income (GRDP) from each administrational level in 2010 from Statistics Korea.

Sustainable Water Index (SWI) in 2010 was illustrated in Figure 1. One of the interesting results in this study is that watersheds where are highly populated showed relatively moderate SWI than remoted or upstream watersheds due to the higher Responsive in spite of the high Pressure. On the other hand, watersheds in densely irrigated areas with moderate population in western lowlands and southwestern island areas showed poor results in SWI. Upstream and mountainous watersheds in Kangwon Province showed low pressure and low response resulting in high SWI. Overall, Pressure index throughout the country had moderate to high level of threat in water use in relatively little differences between regions while Response showed distinctive differences among watersheds resulting in crucial factor in determining SWI index. For the major cities in Korea, we found Incheon showed the highest level of SWI as 0.88, following by Daegu(0.77), Gwangju(0.72), Daejeon(0.68), Seoul (0.64), and Busan (0.54). Among pressure indicators, most of major cities had high impervious areas, high nitrogen loading, BOD, and water consumption while low pressure in water leakage, water use intensity, and fee for water supply and sewerage. Likewise, major cities showed higher rate of water supply and sewerage, alternative water resources (water reuse and rain harvesting) while lower in investment on water supply and sewerage infrastructures than other regions.

Supplementary analysis comparing indices (Pressure, Response and SWI) to local income buttressed the importance of Response index in SWI: regions with high income showed high Response index while the Pressure index was indistinctive to regions. To be specific, as regional income increased, index values increased more distinctive in Response Index (0.21-0.71) than Pressure Index (0.42-0.67). SWI started to be stabilized when local income (GRDP) achieved 9 billion dollars in yearly term. It is unnecessary to decide that local governments under the threshold income should increase their financial capacity but to focus on site-specific conditions consisting Pressure, Response indices and their indicators to achieve sustainable water use.

Figure 2 Relationship between Local Economy and Pressure, Response Index, SWI

Moreover, we conducted principal component analysis to figure out the priority indicators consisting SWI. According to the statistical analysis, we selected seven indicators (environmental areas, long-term runoff variability, groundwater level, effective upstream storage, water leakage, water intake, and investment on water supply) as priorities and simplified index consisted of above indicators showed correlation coefficient (R) of 0.78 with the original SWI, showing the feasibility of using abbreviated index framework.

References

Esty, D. C. et al.. 2005. “2005 Environmental Sustainability Index: Benchmarking National Environmental Stewardship”. New Haven: Yale Center for Environmental Law & Policy.

Hsu, A., L.A. Johnson, and A. Lloyd. 2013. “Measuring Progress: A Practical Guide From the Developers of the Environmental Performance Index (EPI) 2014”. New Haven: Yale Center for Environmental Law & Policy.

Kim Y.J. et al, 2014. Development and Application of Sustainable Water Use Indicators in Korea (I), Korea Environment Institute [Korean]

Nardoo M. et al. 2005. “Handbook on constructing composite indicators: methodology and user guide”. OECD Statistics Working Paper.

Vörösmarty C. J. et al. 2010. “Global threats to human water security and river biodiversity”. Nature 467: 555-561.