3.1 Study Area
Pune city is located at the confluence of two major rivers, the Mula and Mutha. The study area covers the current boundaries of Pune Municipal Corporation (PMC). Pune city has been expanded from 7.74 sq km to a massive 516.18 sq km over the past 70 years. The first expansion was to include the 18 villages in 1958, followed by merging 23 villages out of the proposed 38 villages in 1997. The Maharashtra State government proposed a merger of 34 villages in 2014, out of which PMC merged 11 villages with a population of 2.39 lakh and an area of 80.7 sq km in the city's periphery in 2017. After merging the remaining 23 villages recently on June 30, 2021, PMC now has a total of 516.18 sq km of land area within its boundary (Fig. 1). Pune has officially become the city with the largest geographical area in Maharashtra.
3.2 Proposed Geospatial Framework
All the elements of the water cycle, i.e., evapotranspiration, condensation, precipitation, infiltration, surface runoff, river, lakes, soil moisture, and groundwater are interdependent (NWP 2012). Through its multi-dimensional listing, we have tried to cover the entire trajectory from the environmental source of water to supply to distribution in the proposed Geospatial Framework. The proposed framework is designed based on the existing water scenario in Pune city, SDGs, and a review of existing water sustainability templates (national and international). The framework is designed for active management areas (AMAs) to help stakeholders to learn about the water sources that are local and sustainable for instance presence of traditional wells, spring water, green spaces, water bodies, watershed boundaries, wetlands, and groundwater recharge zones.
Water security Geospatial Framework is rich in geographic content and designed with aim of publicly accessible using any of the web browsers. The user may select several thematic layers, overlay, and analyze spatial patterns and relationships between data sets and download the data for offline spatial analysis. The Framework supports various data formats (i.e., shapefiles, GeoTIFF images, KML, and coverage) and projections. The framework is simple, which can be used by people even without a GIS background. The framework aims to allow the user to visualize, download, upload spatial data, prepare maps, investigate, share and communicate and significantly enhance the ability of non-GIS academics and researchers to conduct their research. The proposed Geospatial Framework includes a package of thematic layers (Table 1), geospatial maps (Table 2), and the policies and strategies related to water security (Table 3). The Framework is not static; it can be expanded with more map layers, new policies, and guidelines.
3.3 Application of Geospatial Framework/ Applying cutting-edge technology
We used Geospatial Framework to identify local resources, which could be an alternative source of water to decrease the demand for fresh water in cities. We explored various thematic layers and maps, which were selected from the Geospatial Framework as ready-to-use content, and analyzed the spatial patterns, spatial interconnections, and spatial interdependence between the features visually. Our exploration criteria are listed in table 4.
Most of the peripheral water supply zones in Pune are water-stressed, which need to be examined for better water supply services. Fig.2 shows the water-stressed zones including Balewadi, Baner West, Baner Hill, Sus Sutarwadi, Baner Gaon Zone 2 in the North-Western region, Paranjpe Layout in the Western region, Nyati Enclave in Southern region, Chandan Nagar zone-1, Kharadi zone 1, 2 and 3 in North-Eastern region, and Gliding center/ Hadapsar Gaon in Eastern region. Currently, the city draws the water of the Mutha river from the Khadakwasla reservoir, while dams at Panshet, Varasgaon, and Temghar reservoirs supplement the storage capacity of Khadakwasla. The Katraj and Pashan lakes are not directly used for water supply by the PMC but play an important role in recharging groundwater which is used by thousands of city dwellers. Groundwater supplies also play a significant role in meeting urban water needs. Currently, Pune city is supplied with 13 TMC water annually out of which about 4 TMC of water is extracted from groundwater in Pune city (ACWADAM 2019). It is important to understand the environmentally sensitive water resources for sustainable and equitable urban water supplies, which we assessed using Geospatial Framework at the regional scale.
We created buffers of 5 km, 10 km, 15 km, and 20 km around the PMC boundary for our analysis purpose. We pulled several thematic layers from the proposed Geospatial Framework in ArcGIS 10.5 and demonstrated the application of the Geospatial Framework to solve water issues. The layers included traditional step-wells, aquifers, springs, natural groundwater recharge zones, hilltops and hill-slopes, wetlands, and watershed boundaries in and around Pune city. Our goal is to identify local resources, which could be alternative water sources to decrease the demand for fresh water in cities. The study does not provide design criteria rather explores the potential areas of alternative water resources within the context.
3.3.1 Exploring Traditional step-wells around Pune city
We explored traditional step-wells, which resemble a funnel, with their size decreasing from top to bottom and their sides are lined with a steep flight of steps. The depth of these step-wells varies considerably depending on the level of groundwater as they penetrate deep into the ground to access groundwater. These step-wells have a small surface area at the bottom and considerable depth below ground. Thus the rate of evaporation of water from them is low.
We found several traditional step-wells (Fig. 3) in and around Pune city. We created a buffer of 5 km, 10 km, 15 km, and 20 km around the PMC boundary and overlayed them with step-wells. The study found one step-well i.e. Bhukum stepwell falls within five km, five step-wells between the buffer of 5 to 10 km, 11 step-wells between the buffer of 10 to 15 km, 10 step-wells between the buffer of 15 to 20 km, and several other step-wells fall outside the buffer of 20 km around Pune city (Table 4). The city receives an annual rainfall of 722 mm between June and September, we should effectively use this gift of nature through these community-level structures spread around the city.
The ancient Indian settlement took place not only based upon the presence of rivers, coast, or perennial sources of water but also people settled banking on the presence of these traditional step-wells and rainwater harvesting structures (water tanks). These step-wells were built for water conservations. However, during British rule, many step-wells and water tanks were destroyed as they were found unhygienic and breeding grounds for several diseases. Considering the water shortage today especially in peripheral water supply zones, these step-wells and water storage tanks need to be protected and revived since borewells cannot be the future of the city. The traditional step-wells and rainwater harvesting structures of the past can support our future more sustainably.
3.3.2 Exploring Springs around Pune city
We explored the location of spring water in Pune city, which is majorly ignored as a water source. The use of spring water can fulfill the gap between the municipal water supply and the growing demand across the city. We overlayed the geospatial layer of the Pune spring inventory with the water index layer (ACWADAM 2019), which showed 35 springs, out of which 24 are perennial springs, and 11 are seasonal springs. We identified the presence of springs in many water-stressed zones includes Balewadi, Baner West, Baner Hill, Sus Sutarwadi, Baner Gaon Zone 2 in the North-Western region. ACWADAM (2019) documented discharges and in-situ water quality of these springs and found that spring water is clear and likely to be potable. This water can be used for other non-potable uses too. A detailed water quality assessment is required to check if springs could be an important natural alternative source of water supply at decentralized levels.
3.3.3 Exploring aquifers and recharge zones in Pune city
ACWADAM (2019) documented five types of shallow unconfined (or phreatic) aquifers (Fig. 5), which have a thickness ranging from 10 to 20 m. A comprehensive application of the practice of Managed Aquifer Recharge (MAR) must be designed for the city, based on the main recharge zones identified in each of the five aquifers in the city instead of a random approach to groundwater recharge. The state regulates groundwater at the regional level, but the regulation process to recharge aquifers on a long-term basis demands local interests. Nearly half the area of these five major aquifer recharge areas for Pune city is paved by residential areas, including gated communities, and multistoried apartment buildings. The other half is covered with mixed land use, including open plots, parks, and gardens, open spaces, private residences, commercial infrastructure, educational institutions, and other public and semi-public buildings. Educational institutions and other public and semi-public buildings with large landscaping can be potential areas for MAR, and the guidelines can be customized as per land cover type for groundwater recharge.
3.3.4 Exploring watershed in and around Pune city
Pune is crossed by many rivers and streams, which rise near the Sahyadris. Watershed management is necessary to prevent stormwater runoff, decrease soil erosion and increase groundwater recharge. Protection of the catchments of the watershed clusters would protect the natural recharge zones. There are 30 watersheds in the Pune city limits (Fig. 6). Rapid urbanization has significantly damaged the natural drainage system with the paved surface in all watersheds, which increases the runoff. Therefore, Wright et.al (2021) recommended condensed development and preserve natural recharge zones for maintaining pre-development water balance (Wright et.al 2021). As cities share their watershed boundaries with rural areas, exploring watersheds help decision-makers, knowing the impacts of development on watershed hydrology.
3.3.5 Exploring Nature-Based Solutions (NBS) in and around Pune city
We further explored some Green infrastructure, i.e., green spaces, hill-topes and hill-slopes, wetlands, surface water bodies, agriculture, and forest areas (Fig. 7). Augmenting green spaces improve the natural hydrological systems in urban areas. Expansion of the urban green spaces is an economical and environmentally friendly approach to deal with stormwater runoff and urban flooding. Still, it can also improve the resiliency and sustainability of the city.
The hilltops and hill-slopes occupy nearly 2000 hectares of land in and around Pune city. Hills with afforestation and reforestation to prevent runoff, decrease soil erosion and increase groundwater recharge. As per the land use distribution of Pune city, the total area covered under hills and hill slopes is 5.10%, which governs the city's micro-climate. However, encroachment of hill slopes by informal settlements resulted in the loss of green covers on the hills hence increasing climate change (PMC, 2014). To restore the ecology and enrich the green cover on these hills, regeneration, afforestation for biodiversity, and protection of these hills are necessary. No permission must be granted for constructions on hilltops (where the slope ratio is 1:5) as well as 100ft around the foothills. Further, biodiversity parks have been proposed in six different locations i.e. Baner – Pashan Lake, Pashan Panchwati, Sutarwadi, Hadapsar, Mohammadwadi, and Kondhwa Budruk in the city. Construction on these parks should not be encouraged such an area must be marked as a no-development zone and preserved as an open space. The total area under reserved forest and agriculture is 2905 ha which is 11.91% of the total area that plays a key role in flood risk management. We explored wetlands around the city, which play an important role as they capture rainwater, restrict soil erosion and prevent the impacts of floods. We further explored surface water bodies from the India-WRIS portal and found several small water bodies around PMC, which can be an alternative source of water as community-based water supplies to provide safe drinking water, as the community-based approach significantly increases sustainability.