Urbanwater systems are confronted with significantly changing conditions. Theimpacts of climate change, rapid urbanization, and deteriorating and outdatedinfrastructure aggravate current water challenges of causing flooding, waterscarcity and rehabilitation costs on a scale that will overwhelm the capacitiesof cities.
The World Resource Institute global water-stress rankings (2013)indicate that the ratio of withdrawal to supply in India is 40 to 80 per centand the country experiences high water stress. India has witnessed a rapidincrease in the urban population during the last few decades. All towns andcities currently face the problem of increasing gap between water supply anddemand, which puts pressure on water resources and its supply requirements. By2030, India will have 68 cities with populations of over 1 million.
Growingurban centres, with the concurrent process of urbanization, have broughtseveral issues to the fore, from governance and management of these areas tothe provision of basic civic services. Consequently, there is heavy pressure onwater management.Inthe last two decades, built-up area has grown faster than population in nearlyall of India’s largest cities. A comparison shows that the spatial expansionhas accelerated between 2000 and 2010.
Water supply in most Indian citiesrefers to the layout of infrastructure, i.e. piped water-supply lines, sewagelines, sewage treatment plants (STPs) and layout of drainage lines. If thepiped water supply is inadequate, it is supplemented by private uncontrolledgroundwater extraction, which contributes to pollution of urban aquifers andfall in groundwater levels.
People either dig wells and tube wells on theirproperties for their water needs or buy water from private tankers that, in turn,extract groundwater for sale.Watersources are also highly polluted, limited and subsidized for domesticconsumption. No fixed or standard pricing exists for groundwater extraction.According to a Centre for Science and Environment (CSE) study, the water pricecharged to consumers in metro cities such as Delhi and Bengaluru is Rs 0.35 per1,000 litres and Rs 5 per 1,000 litres respectively, which is fairly low ascompared to actual cost of water supply, i.e. Rs 72 per 1,000 litres and Rs 93per 1,000 litres, respectively.
This leads to increased consumption andwasteful utilization of water in the country. Around 40–90 per cent of thetotal water consumption goes out as wastewater. A CSE survey indicates thatthere is a complete disconnect between water supply and sewage management inIndia. Only 30 per cent of sewage from Indian cities is treated at STPs. Theremainder pollutes natural waterbodies.
Theincreasing demand–supply gap and deteriorating environmental conditions areincreasing the need for environmentally friendly alternatives. It is importantto take up the challenge in controlling and judiciously using natural resourcesto reduce our ecological footprint. Sustainable water management requires aholistic approach toward sustainability along with prudent use of waterresources.Itis clear from the existing situation that a re-focussing of priorities isrequired by way of careful planning to have sustainable water management.Adopting water sensitivity at the stage of planning and designing new andexisting developments can maintain the water cycle by managing the supply anddemand for water, storm water, wastewater and groundwater as well as bringbenefits such as reduction in temperature with respect to climate change andadaptation.Protectinglocal waterbodies (lakes, ponds and wetlands) for supplementary water sources. Storm-water management at public places,including open areas in cities through elements of landscape design (e.
g.vegetated swales and buffer strips, bio-retention systems). Recyclingand reusing wastewater naturally (low cost/low energy) and not treating it as aliability. Increasingwater-conservation approaches at various scales (buildings/ campus)—i.e. byadopting water-efficient fixtures, xeriscaping landscape (i.e.
planting nativespecies) and using water-efficient irrigation methods— thereby minimizing loadon the municipal supply system and groundwater sources. On-site waterconservation with rainwater harvesting (RWH) is also important to reduce waterscarcity. Addingvalue to the social and ecological aspects of areas by planning and designingthe built environment in accordance with community needs and water issues. Connecting the urban water cycle bycollaborating with practitioners of different disciplines to bring differentperspectives and expertise.Thesustainability approach needs to include elements of water quantity, waterquality and ecology, along with community involvement. Therefore, primepotential sustainability factors to facilitate accreditation ofwater-management options with regard to capital cost, resource use, performanceand maintenance are technical, environmental, social and economic elements.Thereis growing realization at the Central/state level that the risk of notaddressing water management in the early stages of planning and design causesconstraints to new development or (re)development, missed opportunities forcost saving, poor quality of urban environment and overall unsustainable urbandevelopment. The need is for more integrated land and water management fromearly stages to reduce the increasing water footprint of urban centres.
CASE STUDY: Scope of RWHintervention, Chandigarh, IndiaChandigarhhas grown rapidly in the last decade (1991–2001). Its population growth ratewas 40 per cent. Its population density of 7,900/ sq. km is one of the highestin the country and it is estimated that its demand for water will grow steeply.By 2025, the city’s demand for water is estimated to be 800 MLD, an increase of58 per cent over the 2011 demand of 494.25 MLD. To ensure long-termsustainability of water sources for the city, RWH is a simple and effectivesolution. It can be done using roads, roundabouts, parks, rooftops, paved areasin almost the entire city.
The storm-water network collects water from roads(15.89 sq. km), rooftops of residential areas, (30.19 sq.
km), shopping areas(3.97 sq. km), and public and institutional buildings (7.94 sq. km).
Thisamounts to over 70 per cent of the total land area. The total quantum of waterthat would be available for recharge annually would be 58 sq. km (area) x1059.3 mm (rainfall) x 0.5 (rainfall coefficient) = 30,720 million litres(18.
46 million gallons per day [MGD]). This is equivalent to almost 90 per centof the total groundwater supply and is available only from tapping thestorm-water-drain network. By careful planning of recharge in parks and greenareas of the city, it would be possible to recharge the entire groundwater thecity takes out.
CASE STUDY: Scope of RWHintervention, Noida, IndiaNoidarequires an unparalleled infrastructure of sustainable water management.However, unregulated and increasingly unsustainable exploitation of aquifershas led to a decline in the water table and deterioration in the quality ofgroundwater in the area. The projected increase in the proportion of hardsurface has further increased runoff while decreasing percolation in the area.The overarching framework of RWH systems that can be implemented in the areadepends on its physical and land-use features. Implementing RWH systems inNoida can contribute significantly to addressing the water demand–supply gap,dealing with waterlogging, flooding and recharging aquifers.
CASE STUDY: Scope of WSUDPintervention, Dwarka, New Delhi, IndiaTheobjective of this case study is to provide sustainable solutions by showcasinginterventions with regard to planning current Indian urban areas. To identifyand analyse the issues and challenges of water management in the India’scapital New Delhi, it is pertinent to note that the population of Delhi hasbeen projected to cross 20 million by 2021. Housing projects such as Dwarkawere envisaged in early 1990 to accommodate approximately one million people.However, the master plan makes no distinction between semi-urban/ peri-urbanareas and areas in transition, such as Dwarka sub-city. Hence, there are nospecific norms or recommendations for these areas, resulting in a widedemand–supply gap. An analysis of the area is conducted in terms of three mainareas: storm-water management, water-supply management and wastewatermanagement.
Dwarka site was analysed with WSUDP approach leading to proposalsand conclusions for each of the water resource integrating with spatialplanning.1.Storm-water management i.Delineation of catchment areas and sub-catchment areas according to trunk drain ii. Calculation of additional runoff dischargein peak hours for storms over 25 years for the respective watersheds by therational formula (Q = CIA). (In the case of Delhi, the intensity of one-hourpeak rainfall is of 90 mm/hr for storms over 25 years.) iii.
Identifying potential sustainablestrategies based on site characteristics and pollution levels according toland-use characteristics in different watersheds iv. Preparation of matricesfor suitable strategies for sustainable urban drainage systems at the watershedand neighbourhood levels (for different land uses) and listing out other environmentalbenefits 2.Water-supply managementi.
Evaluating the current water supply scenario in Dwarka ii. Accessing potential water quantityon-site, comprising runoff, groundwater, wastewater and floodwater iii. Calculating the sustainable quantity ifall the sustainable drainage strategies are applied and regional watercollection in potential site area and present MCD supply is taken intoconsideration iv. Accessing water supply and demand projection by present andprojected water supply cost–benefit scenario3.Wastewater managementi.Calculating the potential grey water that can be reused, listing the currentlyused conventional infrastructure and calculating the cost incurred by using thesame techniques ii. Listing out the different naturaldecentralized techniques that can be used for treatment along with the cost andthe area required for them.
This leads us to propose the purposes for use oftreated wastewater in Dwarka.Water-sensitive planning (city/zonalscale)Water-sensitiveplanning can conserve water resources while offering numerous benefits by wayof improving the urban environment, reducing the danger of flooding, increasingopportunities for recreation and leisure activities, and reducing floodingdamage and cost of drainage systems. Any open space designed according towater-sensitive planning principles provides recreational and visual amenitieswhile filtering runoff that infiltrates to replenish groundwater. It also actsas a detention reservoir designed to reduce flood discharges and pollutantloadings.Thewater cycle in urban areas is lost due to excess construction and paved areas,including in major recharge zones such as lake catchments, riverbanks andwetlands. In addition, contamination of existing water resources with sewageadds to the loss of usable water. The need is to maximize use of open spaces torejuvenate the lost water cycle.
Planning for new areas requires allocatingland uses according to hydro-geographic layout. The placement of openspaces—recreational areas, roads etc.—plays a major role in complying with thewater-sensitive principle.Significanceof open/buffer areas in water-sensitive planning . -Open spaces provide theopportunity to combine the function of public open space with habitat retention(trees and watercourses), pollution abatement and storm-water management. Wetlands/lakes:In densely populated urban areas, lakes and waterbodies are highly contaminatedby the inflow of untreated sewage from areas lacking or having inefficientsanitation services.
These waterbodies and lakes can be planned with a greenbuffer area that can act as a treatment zone. Waterbodies play a major role inthe natural hydrological cycle and offer healthy recreational spaces. Since thesource of the pollution-degrading waterbody may be unknown, these buffer areasact as protective layers.
Recreationalareas: Where open spaces are located in consideration with the natural streamsystem, they can be also used to prevent and mitigate floods by retaining anddetaining storm water and to purify and infiltrate runoff, thus recharginggroundwater with clean water. Storm water that reaches open spaces may be usedfor irrigation and as landscaping elements. Roads and streets: Roads and streetsconstitute up to 70 per cent of the impervious urban area and serve primarilyto transport people and goods. But they also act as important conveyors ofstorm water; in fact, they constitute the major drainage system that serves asan important flow path when the drainage pipes underneath go beyond theircapacity. Inclusion of storm-water streams in urbanfabric: Storm-water streams/ watercourses represent natural drainage lines andtherefore need to be considered part of the storm-water management strategy fora development site. The concept of storm-water streams in urban fabricrecognizes that there are benefits in considering maintenance of water quality,habitat retention and restoration, water conservation and a wider choice ofrecreational opportunities in an integrated fashion.
Watercourses/streams aregenerally linear-shaped spaces and therefore present a longer frontage toadjacent residential development than square or circular plan forms. Theyprovide accessible open spaces to people. Their linear nature also offersopportunities to integrate offroad pedestrian and cycle paths .Water-sensitive designing(neighbourhood/institutional scale)Built-upareas need to be drained to remove surface water. The conventional approach todraining surface water is through underground drainage systems that conveywater from built-up areas. These traditional urban drainage systems focus onquantity as they aim to remove excess water from urban areas as quickly aspossible to avoid flooding. These drainage systems have not been designed withsustainability in mind. The majority do not pay sufficient regard for floodcontrol, water quality, water resources or biodiversity requirements.
Urbandrainage systems have caused an alteration in natural flow patterns, notnecessarily having an effect locally, but causing flooding problems elsewherein the catchment area. Water quality has also become an increasinglysignificant issue as surface run-off from these urban areas results incontamination of the watercourse. Resulting urban flooding is extremelydifficult to resolve and is an important issue that drainage systems must takeinto consideration. In urban areas, continued water management is a necessityand for this to be sustainable, a broad approach to the issue of drainage mustbe adopted. A similar situation is encountered with the conventional wastewatermanagement approach which involves centralized systems of sewerage networks toprovide treatment and disposal.
The conventional technologies of a centralizedsystem of wastewater (sewage) collection and treatment are not justresource-intensive (use of water first to flush, then to carry the waste), butalso capital- and energy- intensive. This further makes scope of recycle/reusebleak as the treated water would again be needed to be conveyed back for reuseand would add to the capital and energy cost. The alternative approach ofdecentralized wastewater management is based on the principle of devolvingapplication so that sewage can be treated affordably and treated wastewater canbe promoted for local reuse.
