Effects of artificial snow on water resources

The issue of the influence of water abstraction for the purposes of artificial snowmaking on the flows of watercourses has not yet been comprehensively addressed in the Czech Republic. If the impact has been addressed, it was in connection with some cases of above-limit water abstraction. Opponents of artificial snowmaking and skiing in general have generalized these individual cases so that all abstractions for artificial snowmaking have a significant impact on the decrease in flows. In fact, ski resort operators have pointed to the fact that these were random individual cases of irresponsible behaviour, which are beyond their control, similarly to other water consumers.

What are the actual impacts of water abstraction for artificial snowmaking on watercourse flows?

As part of the research, the impact on several Krkonoše streams in the Rokytnice nad Jizerou, Špindlerův Mlýn, Pec pod Sněžkou, and Janské Lázně areas was monitored in 2017–2020. The size of winter flows is usually affected by thaw. If it does not freeze for a long time, and colder periods alternate with thaw and the snow melts, the streams have enough water. On the other hand, in the case of prolonged frosts, flows are low and water abstraction from streams is not desirable. A similar situation occurs when the autumn low flow period extends into winter. If there is enough water flowing in the streams, water abstraction for artificial snowmaking is not a problem. The natural variability of flow fluctuations, caused by water level fluctuations due to natural water level increase/decrease, is more pronounced than changes caused by water abstractions for technical snowmaking purposes. On the other hand, during periods of low flow, a problem may occur.

Detailed insight

The ratio between the permitted maximum amount of water abstracted and the value of the instantaneous flow (at low flow rates, the relation to the value of the minimum residual flow rate) is essential for the possible magnitude of the influence of individual water abstractions. If this ratio is large, then the impact of water abstraction approaching the permitted values may be significant. As watercourse flow increases, the significance of this ratio decreases and the impact of water abstractions is less significant.

Usually, water abstractions are in units of per cent of the flowing water volume. For the worst cases on the Krkonoše streams, the median of the ratios of possible instantaneous abstractions and the minimum residual volume reaches 25% (i.e., on half of the streams, up to 25% of the flowing water can be abstracted); in extreme cases, the ratio is 60% (i.e., 20 l/s within the permitted instantaneous abstraction at a minimum residual flow of 13 l/s). As already mentioned, in reality, the impact is significantly smaller. If we apply the permitted values for the highest abstraction then, for example, at a flow rate of 60 l/s and using the permitted instantaneous abstraction of 20 l/s, the ratio is 33%; at a flow rate of 15 l/s and the compliance of the minimum residual flow rate of 13 l/s, the ratio is 13%.

The course of flows in December 2019 on Svatopetrský potok in Špindlerův Mlýn. The difference between the blue and red curves on 10 and 11 December shows the effect of water abstraction on watercourses at normal flows.

Permits to abstract water are mostly obeyed

From the point of view of compliance with the permitted limits for water abstraction, an analysis of water abstractions greater than 500 m3/month from the Krkonoše region was done for data from 2015–2019. During this period, most of the water abstraction took place according to the set limits, with occasional exceedance of the limits.