Water is life, and one single drop of water is really important. However, water-related issues are arising globally at the moment. This article will elaborate more on the importance of nature-based solutions and payment for environmental service in water sustainability by delving deeper into the practices that society could implement and lessons learning from the various approaches.
As we know, water insecurity is exacerbated by increasing global water demands, population growth, agricultural demand expansion to meet food security requirements, fast-growing urbanization, and climate change. Water insecurity is becoming more uncertain as climate change alters the global water cycle, including increased frequency and severity of extreme events such as floods and droughts . This crisis appears to be deteriorating, as global water demand is expected to increase by 55% from 2000 to 2050, driven by increases in manufacturing (400% above current levels), electricity (140 %), and domestic use (130 %). By 2050, it is expected that 70% of the world’s population will live in urban areas, which typically consume more water. Globally, projections indicate that water demand will soon exceed reliable water supply .
Nature plays an essential role in protecting water supplies by controlling water flow, maintaining water quality, and mitigating natural disasters. Water insecurity is increasing, and nature-based solutions (NBS) can address some key water security challenges. For the provision and regulation of water, NBS involves managing ecosystems to mimic or optimize natural processes, such as vegetation, soils, wetlands, water bodies, and even groundwater aquifers. Adopting NBS for water necessitates a paradigm shift in thinking from demand to supply-oriented water management and planning, where vital ecosystems such as forests are regarded as users and as regulators of freshwater. Based on , the integration of NBS shows promise for addressing water scarcity through supply-side management, particularly by increasing water quality and groundwater recharge.
On a larger scale, water in nature represents a large cycle maintained by natural processes that are disrupted by artificial water systems and urbanization. As a result, water has been forced into the linear model of “take-make-consume-dispose,” which is economically unsustainable and results in a gradual degradation of water quality as it moves through the system. The transition to circular water systems necessitates the refurbishment of water infrastructure, the use of cutting-edge technology, and the incorporation of nature-based ecosystems into grey infrastructure (i.e. hybrid infrastructure). NBS can be considered an umbrella concept for the other concepts, with a robust solution-oriented orientation and biodiversity at its heart .
The benefits are delivered by NBS through green open spaces (e.g., urban parks), green/blue infrastructures (e.g., wetlands, river parks, rain gardens), and structural levels components like green roofs or green walls. For example, addressing water challenges through NBS, i.e., flood risks, droughts, water pollution, freshwater withdrawals, or difficulties related to stormwater and urban water management, promotes the development of multifunctional landscapes, e.g., river parks with the potential to improve human well-being, physical and mental health. From the academic observation,  stated that Blue-green infrastructures are one of the most widely known ways to implement NBS. Blue-green infrastructures are essential components of (future) urban regional planning and as networks of (artificial) natural spaces that are strategically planned in cities landscape. Accordingly, ‘green’ infrastructure components are critical in creating a balanced microclimate in cities. Trees, for instance, mitigate flood risks and the effects of urban heat islands, while pocket parks and streams both architecturally attract people and provide space to alleviate mental aspects of urban stress. Moreover, green rooftops serve several purposes within blue-green infrastructures, including municipal gardening and rainwater collection. In addition, a water source extracted from rainwater, stormwater, and treated wastewater in a city’s sustainable blue infrastructure would relieve or replace grey infrastructure.
More nascent NBS in water utilization is the greywater (GW) reuse that could play a fundamental role, converting a significant fraction of wastewater from a waste to a valuable water resource. Because they are based on a vegetated porous medium in which water flows either vertically or horizontally, GW treatment employing green walls and green roofs can be considered an adaptation of subsurface flow constructed wetlands. The optimization of NBS removal processes entails the selection of appropriate plant species and substrates for growth, the determination of optimal hydraulic parameters, and the establishment of appropriate operating conditions. Green walls and green roofs are similar to reed beds in that GW percolates through planted pots filled with a combination of granular materials such as sand, grow stone, vermiculite, phytofoam, expanded clay, coco coir, and perlite . Urban green infrastructure reintroduces and regulates hydrological pathways at the land-water interface, thus regulating the fate of precipitation, including runoff and groundwater recharge. Furthermore, an urban green building could definitely increase urban climates by shading and the cooling effects of evaporation, thus enhancing citizens’ quality of life as a co-benefit.
Another NBS example is the sponge city concept and program, which aim to improve urban water supplies on a large scale, primarily through the deployment of green infrastructure approaches in urban landscapes. Green roofs, walls, and permeable pavement are all examples of measures, as is the revitalization of degraded lakes and wetlands that absorb excess rainwater. The runoff is then collected and certain pollutants are removed using rain gardens and bio-retention swales . A portion of this water is then returned to the natural system and preserved, ensuring that irrigation and cleaning water are accessible during droughts.
Furthermore, it is interesting to highlight the dew for water availability for seedlings, which supports plant growths. According to Tomaszkiewicz , evapotranspiration could indeed surpass precipitation and irrigation, implying that dew uptake is sufficient to meet the increased water demand. Dew, which is formed when atmospheric moisture condenses on a surface, is shown to have irrigation potential. Thus, there seems to be a premise for harvesting water from the atmosphere. In Spain, a single-wall polypropylene tree shelter demonstrated the efficacy of dew harvesting by increasing the soil moisture content. Because dew harvesting systems are self-contained, inexpensive, and simple to construct, they can effectively reduce seedling mortality.
On top of that, water availability, accessibility, and security through NBS contribute towards goals in SDG 6 (on water), resulting in overall benefits from increased water resources. Aside from NBS, there are various approaches to managing water supply, such as demand-side management, water quality enhancement, and re-use with grey infrastructure improvement. Also, exploring the NBS can be sourced to the local and indigenous knowledge that exists in the society. And with the combination of ecological engineering, a developed NBS infrastructure can be arranged appropriately. Thus, respecting the local value of nature and water management. It also denotes that, referring to , to conserve or increase the quality of catchment areas (watershed), different land management techniques should be employed.
In conclusion, as we observe nature, its structure and so forth, we just need to adjust our built development in the frame of adaptation and mitigation strategies. NBS is the obvious answer to overcome the water crisis. Therefore, together we could achieve a win-win solution for water sustainability, as we are human beings respecting the value of water. Let us do the actions! Water is a priceless gift of nature, thus, save it for the future.
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