A river that flows for people and nature
What automatically comes to mind when a river is mentioned, is flowing waters. We all know rivers have water flows. Even the little children, as they place small paper made boats onto the water and watch in fascination as it moves away.
Flows imply movement from point A to point B anywhere along the river from upstream to downstream. Some of us make use of this flow as we throw rubbish in and watch it flow away from our houses, out of sight to become someone else’s problem. Loggers also use the rivers as an easy means to transport logs from upriver down to a downstream log pond area. So, we all know there are flows in river.
What actually constitutes as a river flow and how important are these flows?
Most of us also know to a certain extent that having flows in a river is important but if you ask why, the most apparent answer would be “no flow, no water – lah”. However, flows in a river have so many more functions than just provision of water.
Firstly, it is important to know that a river flow is not constant. Every river has a flow pattern – called its natural flow regime, depending on its location, size and season. A typical natural flow pattern would consist of high flows, low flows and even natural floods.
This pattern or flow regime greatly influences the river’s ecosystem. It controls the key environmental factors that support life within the river – water chemistry, physical habitat, biological composition and interactions.
Therefore a river’s flow is also known as the master variable of a river’s ecosystem. It is like having a master button to control your house – how cold it is, how much air flows through, how many people it can fit, the types of people it houses, how big or small your house can get and whether the people there will live healthy and peacefully or vice versa.
Why are each of the natural flow pattern important?
So how does this ‘master controller’ work? A river flow is like the blood that flows in our body, carrying all our life’s necessary oxygen, nutrients and waste. It carries sediment to the downstream to form the deltas and land mass. It transports nutrients such as seeds and organic matter for aquatic organisms’ food or propagation of aquatic plants. It transports fish eggs for spawning. In some cases, the arrival of flows such as floods also acts as a trigger to initiate fish spawning.
Studies of the big-mouthed shad, or more locally known as Terubok has suggested that the presence or abundance of this fish in Batang Lupar river is also affected by the river’s flow of inland waters. All these support life and the ecosystem functions. Some of these functions occur only during certain time of the flow pattern.
Therefore the timing, quantity and quality of flow are important for specific functions within a river’s ecosystem. The flows that support the ecological functions are also known as environmental flows. In order to keep the rivers as alive and as near to its natural state as possible, environmental flows needs to be sustained as much as possible in altered rivers.
What should we watch out for and manage in terms of impacts?
The natural flows of rivers can be disrupted when changes are imposed on the rivers e.g. excessive dumping of materials and rubbish, changes to the river channels, excessive sediment built up due to pollution from uncontrolled land uses. However, the most significant disruption to a river’s natural flow can be caused by infrastructure development such as levees and dams.
A dam cuts off a river’s natural flow and imposes a changed downstream flow according to how much water, when and how good is the water it releases. It can change the entire river ecosystem from upstream to downstream if not properly managed.
In the Mississippi River, in Colorado USA, sediment loads reduced significantly causing an increasing loss of land at the Mississippi delta and making the coastal areas more vulnerable to floods and subsidence. This means that we have to be careful about the alterations that we impose on a river.
Infrastructure development on rivers should be built where it is necessary only and take into consideration the importance of flows, the ecological functions that river flows play and integrate sound considerations for sustaining flows at the quality, quantity and timing that it is needed, in particular the environmental flows.
The Youth Green X-Change is a youth environmental awareness programme set up in 2014 by Natural Resources and Environment Board Sarawak, Angkatan Zaman Mansang Sarawak, World Wide Fund For Nature (WWF) Malaysia, Environment Department Sarawak, Teachers Training Institute Batu Lintang Campus and Trienekens (Sarawak) Sdn Bhd.