Introduction
The pond ecosystem underpins economic prosperity, social well-being, and environmental sustainability, predominantly in agricultural developing economies. Healthy pond ecosystems are critical for achieving several sustainable development goals (SDGs) through numerous ecosystem services.
They cover more of the Earth’s surface than lakes and provide a variety of ecosystem services, such as flood alleviation, aquifer recharge, nutrient retention, carbon sequestration, mitigation of urban heat islands (UHIs), fish production, and habitat conservation. Nevertheless, increased anthropogenic stresses (e.g., urban expansion and agricultural intensification) driven by population growth and resource demand have led to a decline in the number of pond ecosystems. The emerging risks of bioinvasion (invasive species) and climate change are also threatening the provision of pond ecosystem services.
In India, the loss of 80,128 ponds/tanks (2006-2007) resulted in the loss of 1.95 million hectares of irrigation potential (Ministry of Jal Shakti, India (MoJS2022), http://mowr.gov.in/). The loss of ponds is particularly threatening to the water and food security of developing nations, where freshwater bodies cover ≤1.4% of the land compared to 3.5% in developed countries.
Despite the ecological and social benefits, ponds have been largely excluded from several international and national legislations and commitments that target freshwater ecosystem protection and conservation. Restoration and management efforts are primarily directed towards larger water bodies and wetlands of national importance or are part of a national protected area network.
Distribution of Ponds and Existing Challenges
Ponds are century-old traditional water harvesting structures that are central to the settlement pattern of India. According to the 5th census of the minor irrigation scheme (2013–2014), ponds/tanks contribute 41%, which is the largest share in the surface flow minor irrigation scheme of India. In 2017–2018, the Space Application Center of India mapped 231,195 water bodies and wetlands in the country, covering an area of 15.98 million hectares, which accounts for 4.86% of the total geographical area of India.
Figure 2 Distribution of ponds and tanks in India (2017-2018)
The distribution of ponds and tanks (Fig. 2) indicates that two-thirds (i.e., 65.67%; 151,815 ponds/tanks) of the total water bodies and wetlands mapped in the country contribute 11.4% of the total mapped area. India’s first water census report (2023) by the Ministry of Jal Shakti further reports that ponds account for 60% and tanks account for 15% of the total water bodies (242,540) in India, outnumbering the larger water bodies in the country. Apart from legal challenges such as land use change and encroachment, ponds are subjected to numerous physical, chemical, and biological pressures. Eutrophication, thermal pollution, siltation, exposure to emerging contaminants, pond acidification, and bioinvasion largely contribute to pond degradation and consequent biodiversity loss.
Consequently, in India, 15% of the water bodies (mainly ponds and tanks) under the minor irrigation scheme-2015 remain unused and non-functional (MoJS, -http:// mowr.gov.in/). Urbanization has emerged as the major cause of pond degradation and encroachment in India.
Pond Restoration and Enabling Environment
A proposed framework for pond restoration and enabling environment is illustrated in Figure 3.
3.1 Inventorying and Monitoring Ponds
The central and state pollution control boards of India monitor the physicochemical characteristics of only 97 ponds and 123 tanks (CPCB 2020). A reliable inventory of ponds/tanks at different geographical scales is critical for comprehending the biogeochemical cycles and addressing the associated social, environmental, and economic issues. With the availability of advanced, high-resolution light detection and ranging (LiDAR), hyperspectral, and multispectral satellite images, large-scale mapping of the small and scattered ponds/tanks becomes feasible. Hydrological modelling is frequently used to remotely monitor hydroperiod alterations. The use of Narrow-band Internet of Things (NB-IoT) for real-time aquaculture pond water quality monitoring provides technical assistance in establishing regulations and determining pond management strategies.
3.2 Hydroperiod Modification and Erosion Control
Principally, the balance between water depth and hydroperiod needs to be maintained for the protection of pond habitat. At the pond scale, commonly used measures to modify the hydroperiod include the removal of sludge and sediment (desiltation), elimination of shading effects, mowing of vegetation (de-weeding), and algal control. Structural measures such as silt barriers, sediment traps, stabilising earthen embankments, sediment detention basins, and re/ afforestation could be promoted at both the pond scale and landscape scale to control soil erosion and sedimentation.
3.3 Nature‐Based Solutions (NBS) for Pollution Control
Nature-based solutions (NBS) offer a sustainable and cost-effective approach to restoring natural processes by altering the fluxes of nutrients, sediment, water, and other pollutants. They also contribute to several SDG-2030 targets. Commonly used NBS consist of green infrastructure (e.g., constructed wetlands and vegetated buffer strips), ecosystem-based management (e.g., blue-green network), mitigation and adaptation (e.g., reforestation and conservation tillage practices). The application of one or more NBS, together with appropriate grey infrastructure, can provide landscape- scale restoration of ponds. Landscape- scale restoration also involves the use of green spaces such as parks and vegetative buffer strips, which enhance infiltration (aquifer recharge) and bio-retention (i.e., nutrients and sediments). They act as barriers to urban stormwater runoff and the inflow of pollutants into the receiving water body. Source water protection through NBS is less costly than managing downstream impacts.
3.4 Incentives, Government policies, and Legal Options
- A uniform waterbody classification system applicable to all the water bodies (including small ponds) is vital to ensure better administration and monitoring in all the states. Also, a comprehensive national pond data- base incorporating states and local bodies is required to facilitate objective policymaking and appropriate intervention at different levels.
- Integrate pond conservation into sectoral development plans and sustainable development goals. A coordinated inter-ministerial and inter- departmental approach can formulate a single comprehensive scheme to conserve and restore the ponds at the local level (Top-down approach).
- Appropriate demarcation of pond boundaries and its inclusion as a municipal asset under the land records by states can be a vital step to put off pond encroachment. The No Net Loss (NNL) policy can be effectively used as a regulatory instrument to mitigate (i.e., minimise the impact) and offset (i.e., compensate) the unavoidable losses due to existing or proposed development activity
- Government incentives to promote sustainable business models supporting pond restoration, conservation, and local economy.
- Linking the circular economy (CE) and aquatic ecosystem is vital for the future provision of natural resources (e.g., water, food, nutrients), energy (e.g., biomass, biofuel), and ecosystem services.
- Inclusion of local stakeholders in pond-related decision making, policy formulation, and action plans to establish a linkage between the pond ecosystem and various stakeholders (bottom-up approach) ensuring long-term conservation of ponds.
Views expressed by: Dr. Shweta Yadav, National Institute of Hydrology, Roorkee-247667, Uttarakhand, India Email: shwtdv@gmail.com
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