Supporting water flow regulation accounting through hydrological modelling

Water is commonly treated and discussed as a provisioning service, possibly because water is generally perceived as the product of a basin. However, ecosystems do not create water; they move and modify water flows. An ecosystem’s ability to retain water coming from precipitation or melting snow through vegetation canopy storage, infiltration to soil or recharge to geological structure is considered to be one of the most important regulating ecosystem services provided and is therefore an important part of natural capital. The effects of this regulation are water storage in landscape and a slower release of water to streams, which means possible peaks of high water flows are attenuated and low flows during the periods between precipitation events are higher and staler. We locally substitute this service using artificial structures such as big reservoirs.

Many of these processes related to water flow regulation are difficult, or even impossible, to measure. Moreover, regulating ecosystem services are often quantified as the difference between the stage where the service is actually provided and a hypothetical scenario where the service would not be provided. For this purpose, a modelling approach is needed. Hydrological models simplify processes through which water flow from precipitation is modified by mathematical equations. These models require a lot of input data (such as meteorological data, data concerning soil properties, vegetation type, terrain, etc.) and need to be properly calibrated against measured data (such as measured stream flow, evapotranspiration or soil moisture) so that as many relevant model outputs as possible may be obtained. Subsequently we can estimate the effect of an ecosystem on water flow regulation by removing it from a model and assessing the difference from changes in outputs of high flows or low flows and their frequency. These variables can then be connected to economical units such as households, agriculture or industry by providing, for example, water flow regulation for flood damage reduction, or maintenance flow for electricity production or for recreational activities.

Estimated contribution to high flow regulation of the main ecosystem types in the Czech part of the Odra river basin