Ha2 20702099

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~~1-1-1-1-1-1-1-1-1-1-r jan feb mar apr may jun jul aug sep oct nov dec

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Fig. 7.6. Mean runoff combined with the 10th and 90th percentile of runoff distribution at Lobith for the current situation and projected according to the SRES HA-2 scenario, 2070-2099.

may lead to increased demand for water for irrigation purposes, especially for soils with low water-storage capacities. The Netherlands could face the desiccation of most of its wetland areas or be forced increasingly to rely on the Rhine to maintain present water levels. Especially during periods of low river discharge, groundwater aquifers could be affected by increased saltwater intrusion as sea level rises. Given a possible 4°C increase in temperature, and a rise in the alpine snow line of 500-700 m in the summer, the flow of the Rhine could decline by 10% during this season. Below are the major expected impacts of climate change on the human environment, ecosystems, food security and industry (see also NWP, 2003).

The environment

The impacts and effects of extreme peak flows can be enormous. Flooding and subsequent damage and losses will occur along river stretches where design criteria for flood protection are exceeded. Historical flood records in Germany and The Netherlands illustrate that natural disasters can devastate prosperous (local) societies and economies for a long period of time.

Both high and low discharges can result in damage to habitats. Peak flows can result in disturbance and flushing of macrofauna and pollution of groundwater. Low discharges will have consequences for the availability of water for drinking, irrigation and nature, for example by lowering groundwater tables. On the other hand, a more dynamic river flow could also result in a more diverse environment, stimulating biodiversity.

Assuming that the total loads of pollutants via point and diffuse sources will remain the same, concentrations of dissolved substances will increase during low water flows. Although some reduction of the total pollutant load may be realized, concentrations of pollutants may reach levels that are toxic for river organisms and will cause problems for the supply of drinking and irrigation water. Increased levels of organic compounds, including algal biomass, might cause low oxygen levels and kill river fauna. An increase in temperature can amplify this effect. An increase of water temperature might also affect the abundance and diversity of riverine species (disappearance of sensitive species, colonization by exotic species). Finally, increased intrusion of salt water during low discharges can impair water quality in downstream stretches of the river.

Food security

The relationship between the changed discharge regime of the River Rhine and food production in the countries bordering the Rhine is complex. In the Rhine Basin in general, the importance of river water for irrigation is much less than in the arid regions of the world. However, an increased risk of salinization in the downstream part of the Rhine Basin will be of major concern in periods of reduced flow, as this will limit the use of Rhine water for irrigation.

In the EU agriculture accounts for only a small part of the GDP. Moreover, the Rhine catchment already suffers from huge overcapacity of agriculture, and subsidies are devoted to controlling overproduction. Therefore the vulnerability of the overall economy to changes that affect agriculture is low. The aim of the present EU agriculture policy is to focus more on limitation than on intensification of agriculture, with a shift towards sustainable production. This will be accomplished by taking marginal lands out of production and the stimulation of organic farming (European Commission, 2003). In general, the effects of climate change (increase in CO2, rise in average temperature and a net increase in precipitation) in principle are expected to have a positive effect on crop production. An increased risk and probability of water stress in late summer and early autumn will be compensated largely by an earlier start of the growing season.

Industry

Water is an important agent for cooling processes in electricity production (both nuclear and conventional production of electricity) and in other heavy industries. The major industrial regions in Germany in particular depend very much on the hydrolog-ical regime of the River Rhine. Increased drought during the summer seasons, as well as increased water temperatures, might seriously hamper these industrial processes.

Inland navigation plays a major role in bulk transport and is becoming increasingly important for container transport. Low water levels result in unreliable transport means, because of the link with the allowable draught of the vessels. Peak flows will hamper navigation because high water levels can also result in navigation restrictions.

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