Text av Magdalena Bieroza.
Water in agricultural landscapes - Don't throw the soil and nutrients out with the stormwater
Water in agricultural landscape is needed for plant growth and sustaining the lives of rural communities. However, too much water in the form of stormwater can have negative effects both on agricultural production and environment.
To make agricultural soils fit for production, water flow has been changing over centauries leading in general to shortening and straightening of streams and introducing artificial drainage in the form of open ditches and subsurface pipes.
All these changes led to much faster water flow through agricultural landscape compared to more natural landscapes, and rapid changes in flow. This increased flashiness of the agricultural landscape together with intensive cultivation and use of fertilizers, have led to an increase in soil erosion and nutrient (mainly phosphorus and nitrogen) leaching, leading to increased stream export of these resources from the agricultural landscape and their accumulation in the downstream ecosystems: larger rivers, lakes and seas.
These downstream ecosystems suffer from high nutrient and sediment concentrations that over a long time lead to eutrophication, hypoxia (oxygen depletion) and loss in biological production e.g. fish kills. These changes in agricultural landscapes lead to a paradoxical situation in which by trying to reduce something bad (stormwater) we also get rid of something good (soils and nutrients), as in the popular proverb advising not to throw the baby out with the bathwater.
So how not to throw the soil and nutrients out with the stormwater in agricultural landscapes?
Water quality scientists and managers try to solve this challenge by understanding where from, when and how much sediments and nutrients are delivered from agricultural landscapes to streams and rivers and how to reduce this export. Water quality records for agricultural streams and rivers provide many answers to those questions. Long-term records can tell us how much sediments and nutrients have been exported from agricultural landscapes historically in response to large-scale land use and climate changes.
Shorter but more frequently collected water quality data, can on the other hand provide clues on where and when sediments and nutrients are coming from. Both long-term, coarse and shorter, high-frequency water quality records can help us to evaluate the effectiveness of land management interventions aimed at reducing soil erosion and nutrient export.
This talk summarizes the effects of agriculture on water quality through the lens of water quality records from large and small agricultural catchments around Europe.