Assessment of Environmental Water Security of an Asian Deltaic Megacity and Its Peri-Urban Wetland Areas

Abstract

Achieving urban water security requires sustaining the trade-offs between the exploitation of water/environmental resources and ecosystem services. This achievement not only reduces the pollution and contamination in the environment, level of water stress, but also secures good ambient water quality and future for people’s well-being and livelihoods. Changes in land use and land cover and growth of impervious structures can immediately generate severe ecological and social issues and increase the level of natural or manmade risks, affecting the condition of ecosystem services within and in the vicinity of an urban region. As a result of these transformations and further exploitation, due to the growing anthropogenic pressure, surface water and groundwater quality can be deteriorated compared to ambient water quality standards (for both chemical and biological pollutants). Based on land use and land cover (LULC) data retrieved from remote sensing interpretation, we computed the changes of the ecosystem service values (ESV) associated with the LULC dynamics, water quality and, finally, urban water security during the pre- and post-monsoon periods of 2009, 2014 and 2019 in Kolkata, an Asian deltaic megacity, and its peri-urban wetlands named East Kolkata Wetlands (EKW). The area under wetlands reduced comprehensively in 2009–2019 due to the conversion of wetlands into various other classes such as urban settlement, etc. The quality of surface water bodies (such as rivers, lakes, canals and inland wetlands) deteriorated. The groundwater quality is still under control, but the presence of arsenic, manganese and other metals are a clear indication of urban expansion and related activities in the area. As a result, there was a change in the ESV during this timeframe. In the pre-monsoon period, there was an increase in total ESV from US$53.14 million in 2009 to US$53.36 million and US$59.01 million in 2014 and 2019, respectively. In the post-monsoon period, the ESV decreased from US$67.42 million in 2009 to US$64.13 and US$61.89 million in 2014 and 2019, respectively. These changes can be attributed to the peri-urban wetlands and the benefits or services arising out of them that contribute more than 50% of the total ESV. This study found that the area under wetlands has reduced comprehensively in the past 10 years due to the conversion of wetlands for various other uses such as urban expansion of the Kolkata City, but still, this peri-urban wetland supports the urban water security by providing sufficient ecosystem services. In conclusion, the transformation in extent of the water-related ecosystem is a crucial indicator of urban water security, which also measures the quantity of water contained in various water-related ecosystems. Quantitative analysis of the LULC change, hence, is important for studying the corresponding impact on the ecosystem service value (ESV) and water quality that helps in decision-making in securing urban water future and ecosystem conservation.

A transdisciplinary and collaborative urban water security framework: Developed through an interdisciplinary study in Kolkata, India

“…At the same time, analysis of arsenic (As) in groundwater samples from across Kolkata failed to detect concentrations >10 μg/L from natural processes. That means there is a continuous source of contamination of groundwater from unregulated industrial activities, which is decreasing water security for millions of people slowly but steadily over time (Mukherjee, Sikdar, et al, 2021).…”

“…ii. Urban Environmental Water Security Index (UEWSI) (for details, please see Mukherjee, Sikdar, et al, 2021) The urban environmental water security index (UEWSI) has been calculated based on results of LULC change analysis between 2009, 2014, and 2019, and Intensity indices (Su et al, 2011;Suja et al, 2013;Tate et al, 2005;Zhou et al, 2014), which explain the degree of change in average ecosystem services value (ESV) in each borough (an administrative block comprising several lowest administrative units called ward) of Kolkata Municipal Corporation and East Kolkata Wetlands for the given period of time. The temporal and spatial variation of the UEWSI was prepared using the following equations:…”

“…Appendix lists a compilation of approaches, dimensions, and issues of quantifying UWS. Although these all contribute to great advances within the area of water security, most fail to consider social perspectives and their relationship with the biophysical environment (Mukherjee et al, 2022; Mukherjee, Sikdar, et al, 2021; Mukherjee, Sundberg, & Schütt, 2021). Furthermore, they fail to include the affected communities, and their unique experiential knowledge.…”

“…Our UWS framework is there therefore advocate inclusive, collaborative, and transdisciplinary UWS—allowing us to understand the complex web of barriers to and opportunities for assuring water security for all in an urban area. In our previous articles, we have presented parts of our index, with a focus on WaSH for example (Mukherjee et al, 2022; Mukherjee, Sikdar, et al, 2021; Mukherjee, Sundberg, & Schütt, 2021). Here, we discuss the full index with its multiple parts and our full framework.…”

Estimating Combined Effects of Climate Change and Land Cover Change on Water Regulation Services of Urban Wetlands in Valdivia, Chile

“…Critically absent from the literature on the flood‐mitigation services of wetlands are city‐wide studies on how performance of the urban stormwater management system changes when urban wetlands are constructed, restored, or incorporated. Change in the value of water‐regulation service of urban wetlands over is often estimated using simple land‐use or land‐cover change and look‐up tables of water regulation service values according to regional wetland area (G. Li et al., 2022; Mukherjee et al., 2021). Such estimates assume water regulation services absent any details or consideration of the stormwater management system to which they are connected (C. Wang et al., 2018; Y. Wang et al., 2018; Zhang et al., 2020).…”