The Five Dimensions of Water
Dr Dietrich Bartelt, CEO of Future World Technologies, explains why redefining ‘water’ is essential for the sustainable management of river basins
18 Apr 2023 by The Water Diplomat
Independently of the professional discipline from which we analyse water management - whether we are looking at water from the perspective of international water law, financial investments, engineering, or social equity – the current approach focuses too narrowly on ‘water’ as the liquid H₂O. This limited understanding currently stands in the way of reasonable and equitable use of water in a river basin, it is gradually leading to large-scale loss of storage capacity around the world, it is a waste of the huge volumes of financial resources invested in water infrastructure, and it is above all unnecessary from an engineering perspective.
In its natural state, in a river basin, the flow of water links five dimensions to each other: the water (H₂O) that flows, the solids like sediments or stones that are transported in a river, the species like fish or microorganisms, but also flora and fauna for which the river is a natural habitat, the gases and chemistry that are dissolved in the water, and the temperature of the water. Together, these five dimensions are connected and comprise the surface water of a natural river system. The connection is the flow of water in a natural river. Any change in one of the dimensions of this water has an impact on the other four dimensions. .
Present day dam building has an impact on the ecosystem in a river. Since natural rivers are continuously transporting and eroding sediments and stones, the reduction in velocity of water to zero near a dam causes sedimentation and siltation: on average, dams can lose around 1% to 2% of their storage capacity annually to sedimentation and siltation. Globally, we have lost around 50% of the storage capacity that we have built due to sedimentation. According to the World Commission on Dams and the International Commission on Large Dams, the rate of sedimentation and storage loss in existing dams has actually been exceeding the rate of construction of new dams for more than the past 30 years. Sedimentation therefore reduces storage capacity and therefore reduces the value of the infrastructure – whether for water security or for power generation. Sedimentation in the upstream of dams also leads to reduced flood protection downstream, as the sediment normally slows the flow and lessens the amplitude of a wave flowing down a river. Due to reduced flow – as well as by cutting an ecosystem in half – a dam reduces biodiversity, as organisms cannot travel up or down the river, and oxygen levels behind the dam are low. In reservoirs, organic matter accumulates and decomposes anaerobically, contributing to greenhouse gas emissions.
Downstream of the dam, the water flows with the same force but without its normal sediment load, becoming ‘sediment hungry’. It erodes the riverbed immediately below the dam and can in the long term threaten the integrity of the dam wall, as is happening in Kariba dam in Zambia, where a huge scour caused by the erosion is just below the dam about half as deep as deep the height of the dam (more than 80 m high). Further downstream, the nutrients and silt that are normally transported down the river would contribute to the fertility of soils and sustain agriculture. At the coast, the delta suffers from a shortage of sand and silt, leading to a shrinking delta with backward erosion and a further costal erosion, and removing the natural buffer that prevents salt-water infiltration into coastal aquifers and therefore impacts the water quality of the ground water.
None of these negative consequences of the use of water are necessary, if the impact of using and storing water would be compensated at the origin of the impact. It is perfectly possible to construct water storage infrastructure that enables a natural flow of silt down the river, allows flora and fauna to move both upstream and downstream, and eliminates all of the above problems. For instance by applying the improved and continuous sediment management system for the impacted sediments in reservoirs and transferring them to up to 5m diameter Archimedes screws. These can be designed in steps like a ladder along a dam. The screws can be operated in two ways and therefore it is possible to restore the natural flow of a river and during times of fish migration, allow fish to swim upstream.
In fact, operators of dams can generate more power in hydro power screws since with the water and sediment mixture, the sediment laden water has a higher specific weight that just plain water.
The founder of DB Holistic Consulting and DB Sediments GmbH has won international prizes for its design of systems for sustainable sediment management. These are the kinds of solutions that organisations like Future World Technologies envisage applying in order to restore the 350000 km of river beds mentioned at the UN Water Conference in New York, and move the world to a more holistic understanding of water in its natural context.