Several of the Sustainable Development Goals are closely linked to or dependent on river health rather than simply on water. River health relates to the condition and viability of ecosystems in river corridors, generally defined as the land adjacent to rivers. Maintenance of river health depends on river flows, water quality, and the general environment of these corridors.
Of the 10 worst polluted large rivers in the world, nine are in the Asia Pacific region. Most of the region’s rivers where ecosystems have collapsed are those passing though highly urbanized areas. In some cases, these rivers function more like drains and sewers. Yet even in these cases, it is possible to restore the ecosystems to a degree that they become an asset rather than a liability and provide attractive and safe river areas for rest and recreation.
Recent estimates suggest that by 2050 about 3.4 billion people could be residing in water-stressed areas in Asia. East Asia has about 3,000 trillion cubic meters of renewable freshwater, while Southeast Asia has 5,800, South Asia 3,500 and Central Asia 600. But not all of this water is readily available for use, and there is a great imbalance within countries and the region.
A considerable volume of water is being taken from the rivers and lakes in these areas. For example, over 50% of river water is withdrawn for different uses in water-scarce areas of Central Asia.
In Asia, even with controls on demand and improvement in water use efficiency, the demand is already exceeding the sustainable supply and will likely be increased over 40% by 2030 in many areas. This will mean less water is available to meet the minimum environmental requirements of rivers, estimated at 50% of total available renewable water resources. Rivers are already experiencing diminished flows (whether due to over extraction or due to climate variations) or pollution.
The main sources of pollution in any part of the region include point sources such as urban sewer and industrial effluents, and nonpoint sources comprising runoff from dispersed farms. Point sources still account for most of the river pollution in the region.
Despite several initiatives by many governments, and with some improvements in the early years of this century, further improvement in river health quality is proving difficult to achieve. The future is not looking rosy given economic growth targets especially post-COVID-19 development scenarios and climate change impact in the region.
River health is mostly associated with complex urban-rural links of cause and effects in land use, water use/availability, water pollution and water governance, which we often look at individually. To tackle these issues requires a more integrated and cross-sector strategy, sometimes called an Urban-Rural Water Linkages approach.
There is a particular need for coherence between urban water and river basin management. In localities, urban and rural areas can often share a single water resource system in a variety of ways, where groundwater and the rivers are linked as one water resources system. Therefore, what affects the river affects the groundwater, and vice versa; and interventions in urban communities affect the rural population, and vice versa.
There are significant urban-rural connections regarding land use. Changes in rural land cover (such as through deforestation or agricultural practices) will modify the hydrological regime while soil erosion will lead to higher sediment load and higher nutrient levels in rivers. While higher flows can cause more flooding, lower flows will impact the availability of water for urban consumers and the ecosystems. Urban development generally increases runoff, and stormwater drainage reduces the retention capacity of the flood plain that leads to more serious flooding, as we have witnessed in recent years.
In terms of the urban–rural linkages regarding water withdrawals, rural water withdrawal (like for irrigated agriculture) can constrain the water available for domestic and industrial uses in urban areas. Groundwater withdrawal in a large volume for irrigation may cause land subsidence in urban areas. In coastal or estuarine zones, it may even lead to salinity intrusion. Conversely, water withdrawals or basin transfer for urban uses reduce availability of water for peri-urban and rural users.
The urban–rural connections on pollution include poor water supply and sanitation as well as waste management practices in rural areas that degrade the water quality of surface water and groundwater on which others rely. Pollutants from agricultural activities can lead to serious deterioration of surface water and groundwater quality. River pollution damages the riverfront design of urban areas. And of course, urban and industrial wastes degrade the water quality of surface water and groundwater, on which peri-urban or rural livelihood and public health greatly depend.
The large gap in the standard of services between urban and rural areas tends to stem from institutional and governance issues, mainly in terms of investment priorities, planning, implementation, and operation and maintenance. Proper rural water services usually do not exist in many instances resulting in water pollution, while service providers in urban areas operate on a more economically sustainable basis. Urban and rural water services can be integrated in one to reduce urban-rural inequalities and improve environmental sustainability.
The current challenge is that investments in urban and rural water as well as other sectors are widely considered in silos, ignoring the value of one water ecosystem. These investments may produce a quick feasible solution and achieve immediate goals but not necessarily an optimal solution for the long run, especially when these are not compatible and accountable to the local environment.
A suite of measures can be formulated to ameliorate each of the main drivers of river health decline, backed by institutional strengthening to make the benefits more sustainable. Besides accounting for urban or rural water utilities including farming practices, interventions for a green environment in areas such as the river and riparian corridor, wetlands and green parks, and river buffer zones, will provide benefits to river health as well as urban-rural livelihoods.
In the end, looking at both urban and rural environments, and how they are connected, will be needed to address the urgent need to improve river health in Asia and the Pacific.
This article was originally published by the Asian Development Bank