Interconnection of Water Landscape and Society The Impact of Humans on Water Cycle

Water is an integral part of the landscape and cannot be separated from landscape management which is still often neglected. Sufficient supply of drinking water, and water for industrial and irrigation purposes, have always been at the center of the human interest. Depletion of water resources and destruction of vegetation cover have led to vast socioeconomic problems as well as the decline of whole societies (Mesopotamia, North Africa, and India). Water is and always will be a limiting source, thus potentially a cause of international conflicts.

Only recently has our society begun to assess the water sources as important systems of biological as well as socioeconomic values. This has also been reflected in the legislation of some states. In 2000, the most sub stantial piece of water legislation ever produced by the European Commission was implemented, taking into account environmental, economic, and social considera tions to achieve sustainable water management in the European Union. According to this Water Framework Directive, all inland and coastal waters within defined river basin districts must reach at least good status by 2015. Although this has to be considered as a positive step, there is still lack of holistic attitude to the water cycle management. 'Water cycle management' is still understood mainly as a technical approach to the sur face water. The prevention of an anticipated lack of potable water is usually meant to be solved by building large water reservoirs. It is often forgotten that water reservoirs have to be filled with water from the land scape. If the landscape does not have enough water, it is being progressively drained.

Water management has led to substantial changes in water species compositions, water chemism, as well as water bodies' morphology. Plentiful impoundments of watercourses have led to disruption of river continuum, strongly modifying the flow rate as well as temperature regime of the flow. Large rivers all over the world have been shortened to improve their navigability and gain farmland on their banks. It is estimated that reservoirs all over the world retain more than 4.000 km3of water, which is about twice the volume of water stored in world's rivers. They cover an area of about 600 000 km2. Since 2007, the largest hydroelectric river dam in the world is the Three Gorges Dam in China. The reservoir is over 600 km long and can hold 39.3 km3 of water. About 1.13 million people have had to be displaced by the rising waters. Also, by building the Aswan Dam on the river Nile in Egypt, over 90 000

people had to be moved away. The dam was primarily built to stop the floods but it completely changed the hydrology of the whole catchment. The silt which was deposited to it in the yearly floods is now held behind the dam. The decrease of nutrients in the Nile waters lowers the fertility of the Nile floodplain and leads to drop in Mediterranean fishing. Damming the Nile brought the threat of soil salinization as salt from the water used for irrigation has accumulated in the soil and it is not anymore washed out by floods. Stopping the natural flow of the Nile has caused erosion of farmland down river due to lack of new sediments from floods. The ecological and economic impacts of these measures on the Nile delta are vast. Due to reduction of silt brought by the river into the delta, damming Nile resulted in loss of water fertility, loss of the brackish water lake fishery, inundation of some farmland with seawater, and erosion of coastlines. Lowering the river outflow has also caused an increase in the salinity of the Mediterranean Sea.

However, there are also examples of positive atti tudes, for example from Australia, where problems with water have reached catastrophic consequences. Integrated water cycle management (IWCM) guidelines for New South Wales local water utilities propose a combined system of water cycle management of water supply, sewerage, and storm water so that water is used optimally. In the Thurgoona Campus of Charles Sturt University in New South Wales, rainwater is collected and stored during the Southern Hemisphere's winter and spring. Runoff water and 'grey water', which origi nates in kitchen sinks, showers, and laundries, is collected in swales and treated in wetlands. The col lected water flows into three interconnected retention basins, from which water is moved via windmill and a solar pump to storage dams at the top of the hill. Water is released from these dams into the waterways when required. Composting toilets are used to treat sewerage on site, and make the connection to the town sewerage scheme unnecessary. The water recycling system has functioned since 1996.

Also some historical attitudes to the water systems have proved to both function economically and positively influence the landscape. Since the Middle Ages, large systems of artificial ponds were constructed especially in the Middle Europe. These hydrological systems brought a whole range of positive effects. It largely improved the retention capacity of the landscape with no damage to the ecosystems, proposing in parallel a lot of economical advantages. Draining water from the marshes and wet lands into the predominantly shallow (1-2 m deep) ponds lead to gaining of valuable farmland. Retained water was used for fishing as well as energy production, water accumu lation, etc. Fishpond systems also played an important role in flood prevention, ameliorating and retarding the flood wave.

A nice example of such water management is the fishpond systems in TreboĆ¼ Basin (MaB UNESCO Biosphere Reserve), with its largest pond (area of about 5 km ) in Central Europe called Rozumberk (see Figures 1 and 2). This pond alone, with its normal volume of water being

Figure 1 A scheme of artificial ponds system in the Trebon Basin (Czech Republic) constructed from the sixteenth to the nineteenth century. The ponds are interconnected by an artificial channel (Zlata stoka) which is about 42 km long and supplies water to ponds. The numbers show surface area of individual ponds in hectare.

Figure 1 A scheme of artificial ponds system in the Trebon Basin (Czech Republic) constructed from the sixteenth to the nineteenth century. The ponds are interconnected by an artificial channel (Zlata stoka) which is about 42 km long and supplies water to ponds. The numbers show surface area of individual ponds in hectare.

Figure 2 Trebon Biosphere Reserve. Cultural landscape with artificial lakes-fish ponds. Photo J. Sevcik.

5.6 x 106m3, retained 50-70 x 106m3 of water during the catastrophic floods in 2002. The whole Trebon Basin (c. 700 km ) with its plentiful fishponds retained about 2 2 0-2 50 x 106 m3 of water.

0 0

Post a comment