Runoff characteristics

Surface-water hydrology The local surface-water hydrology of the area is important in estahhshing the existing natural drainage and runoff characteristics that must he considered. Other conditions of flooding must also he identified. 

Information on runoff characteristics in alpine regions provides the key to a comprehensive understanding of alpine hydrology. Runoff is both an expression of the complex interplay between precipitation, evaporation and storage changes, and of the close relationship with natural environmental conditions. 

It is apparent from the above that only very few catchment areas in alpine regions have access to runoff data. Consequently, regionalization procedures need to be developed and applied for the purpose of estimating runoff characteristics [42]. In turn, however, the value of such estimates depends on the runoff data available for calibrating these models. This gives rise to the same dilemma mentioned above in connection with mnoff measurement networks In alpine regions with few runoff measurement stations it will be difficult to develop effective regionalization approaches. 

Kling H, Nachtnebel HP, Ftirst J (2005) Water balance regions, climatic water balance and runoff characteristics. Hydrological Atlas of Austria, Plate 7.1, Wien... 

Keywords Artificial snowmaking. Hydropower, Irrigation, Runoff characteristics, Water use... 

The production of electrical energy by storage power plants constitutes the dominant form of water use in the alpine region. Since the use of water by these types of power plants can have a significant impact on runoff characteristics and hence on a wide range of other parameters for rivers and streams, the issue is examined in more detail in the following section. 

Influence of Power Plant Operations on Runoff Characteristics... 

Fig. 2 Functional principle of a storage power plant and its impact on runoff characteristics (acc.

The influence exerted by power plants on runoff characteristics is also clearly illustrated by the daily averages. Over the past 100 years, the number of days with maximum and minimum mean daily runoff on the River Rhone (Porte du Scex) was drastically reduced (Fig. 4c and d). While the runoff limit of 400 m s was exceeded on an average of 45 days per year between 1905 and 1954, between 1955 and 2004 this only occurred on an average of 18 days per year. The change is even more pronounced in small runoffs in the phase with no influence from power plants, the daily mean runoff was less than 50 m s on an average of 54 days per year, whereas in the phase influenced by power plants this only occurred on an average of 2 days per year. 

Fig. 4 Case study Rhone (Porte du Scex, 1905-2004) usable volume in reservoirs in the catchment area and associated changes in runoff characteristics (Data [17, 23])...

The large number of water diversion points, reservoirs, and powerhouses exert an influence on the runoff characteristics along extensive sections of Switzerland s rivers and streams [19, 31]. However, the extent of the influence varies widely not only according to region but also depending on the size of the waterway (cf. Fig. 5). 

An evaluation of the basic data, which for Switzerland are on a scale of 1 200,000 [16, 19], produces the following picture the runoff characteristics of more than 70% of Switzerland s main waterways (excluding lakes) are influenced by anthropogenic use. More than half of these (accounting for 40% of all Swiss... 

Fig. 5 Affected runoff characteristics of Swiss waters. By river stretch, river size, and region. (Data [16, 19])...

In principle, changes in runoff characteristics can be said to occur primarily in Switzerland s main waterways. In the case of tributaries, the ratio of unaffected sections is more than 60% (Fig. 5b), and more than 90% for larger streams (Fig. 5c). This points to the fact that rivers and streams of these dimensions are no longer economically viable for use in electricity generation. However, many unaffected sections of larger streams are situated above the first water diversion point. 

It should be noted that no additional aspects were taken into consideration in this compilation other than the influence on runoff characteristics. Any evaluation of morphological, biological, physical, or chemical parameters would produce a very different pattern. 

They also have an impact on runoff characteristics as well as many physical parameters of rivers and streams. For instance, hydraulic attributes (width of water level, flow velocity, depth, tractive force, or shear stress) and hence the bed-load regime and temperature can alter the natural state. 

Apart from the direct impact of water use on natural runoff characteristics, structural changes on surface waters constitute the most striking visual change in the natural system. 

Unlike the evaluation of sections with affected runoff characteristics, these parameters show that small waterways are more strongly influenced (1.6 obstacles per kilometer) than larger water courses (0.6 obstacles per kilometer). However, settlement areas exert the largest influence (2.5 obstacles per kilometer), which is a logical result of the higher need for flood protection and the related level of structural controls [54]. 

Changes in land use triggered by anthropogenic as well as climate change can also have an indirect effect on quantitative runoff characteristics in alpine catchment areas. 

Figure 8 shows the human-induced effects (darkgrey) that can affect the quantitative runoff characteristics of alpine waters over time and space. For the sake of comparison, this figure also incorporates natural effects (hghtgrey). 

Fig. 8 Overview of natural and anthropogenic influences on runoff characteristics...

Morioka, T. and H.S. Cho (1992). Rainfall runoff characteristics and risk assessment of agro-chemicals used in golf links. Wat. Sci. Tech., 25 77-84. 

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