Authors: Ahimbisibwe Alfred (Uganda) and Clement G Tweh (Liberia)
“Water is Life”
You wake up in the morning some minutes late and you decide to rush through your preparation to be in time for the office. You rush to the bathroom, open the tap and lo… there is no water flowing. Your mind switches to panic mode. Can you go to the office without taking a bath? Or even without brushing your teeth?
This is a disastrous situation that the Saxon Dams Authority strives to avert by ensuring that there is always sufficient supply of high quality drinking water available to households and industry at any time all year round. Participants in the 41st Postgraduate Course of Environment Management for Developing and Emerging countries held an excursion to the Saxon Dams Authority’s drinking water reservoirs in Neunzenhain on 3rd and 4th May 2018 to learn about drinking water supply.
Two staff members of the Saxon Dam’s Authority and Dr. Lothar Paul of the Ecological Station Neunzenhain conducted the excursion. The Saxon Dams Authority manages fresh water resources in the Free State of Saxony of which dams make up 20%, the rest being rivers. They are in charge of 153 reservoirs, 23 of which are for drinking water and the rest for flood control. They also supply drinking water to 40% of Saxony’s population with storage capacity of 100 million m3 of water.
Participants were informed that the Saxon dams Authority supplies drinking water to six regional contractors who distribute water in the various cities in the state. In order to balance demand and supply, some dams are interconnected through tunnel systems or open channels and that the water quality has significantly improved due to strict requirements for purification of flue gas from coal power stations and industries that were previously responsible for acid rain.
Talsperre Neunzenhain II
Neunzenhain dams were constructed to provide drinking water for the city of Chemnitz, which was growing rapidly due to industrialization in the 19th Century. The first dam was built between 1891 and 1893 while Neunzenhain II was built between 1911 and 1914 using natural stones from the region. It is gravity dam whose weight of stones holds back the water. To avoid siltation in this dam, two pre-dams built upstream reduce the sediment load of incoming water. Secondly, 25 km² of the dam’s catchment area is forested giving it the best quality of water. The rivers flowing these forests also carry little sediments. However, every 10 years the Dams Authority does a general de-silting operation to maintain the capacity of the dam.
The Neunzenhain II dam was extensively repaired between 1996 and 2000 making it more robust with more monitoring devices to ensure its life is extended. During these works, a new concrete was built behind the stone wall and a monitoring tunnel also constructed. Important parameters monitored include
- Pressure: Due to high pressure in the water column, water tends to escape below the wall. To mitigate this, ground water below the dam wall is sucked out and drained away.
- Dam displacement: Due to alternating seasons, there is dam displacement especially in summer due to temperature difference on both sides of the dam. A maximum displacement measured is 8mm.
Water can be drawn from five different layers in the reservoir and such thermo-stratification allows for continuous supply of clear water even if silted water enters the dam by drawing water from lower layers, which actually remain clear.
Ecological Research Station Neunzenhain
Participants visited the Ecological Research Station in Neunzehain which was established in 1959 focus on research on drinking water reservoirs. This was after a realization that activities in the surrounding areas of the dams affect the quality of water. It was founded as a hydro-biological field station and they have collected a lot of ecological data on reservoirs.
Dr. Lothar Paul and Ms. Henrike Beesk presented research that is going on at the station on Cyano bacteria in the drinking water reservoirs and other micro organism such as phytoplankton, zooplankton and fish. Cyanobacteria produce toxins which can cause sickness and death in severe circumstances. The team also presented ecological interventions used to maintain the quality of water such as bio-manipulation and sanitization of the catchment. Bio-manipulation involves stocking of predator fishes in the reservoirs such as pike and trout to hunt the smaller fishes thus favouring growth of zooplankton which in turn reduce the phytoplankton that degrade water quality.
- Per capita water demand in Saxony has reduced from 200 m3 to 85 m3 and this is attributed to increased efficiency in use and change in industry to less water intensive industry
- To increase forest resilience, broad leaf tree species have been introduced to the previous coniferous monoculture and this diversity improves forest productivity and resilience.