HydrionisGlobal Water Intelligence
Diagram

Agricultural runoff pathways

Nutrients and pesticides reach water by several routes with very different timescales — which is why land management changes take decades to show up in groundwater.

Agricultural runoff pathways

Nutrients and pesticides reach water by several routes with very different timescales — which is why land management changes take decades to show up in groundwater.

Agricultural runoff pathwaysFertiliser and manure applied to fields reach water three ways. Surface runoff carries phosphorus attached to soil particles into streams within hours of heavy rain. Field drains carry dissolved nitrate to watercourses within days. Leaching carries nitrate down through the soil and unsaturated zone into groundwater, taking years to decades. Each pathway delivers different pollutants on a different timescale.Soil and unsaturated zoneGroundwaterFertiliser and manureSurface runoffhours — phosphorusField drainsdays — nitrateLeachingyears to decades — nitrateStreameutrophicationRiverAquiferlegacy nitrate
Phosphorus travels with soil
It binds to particles, so it arrives with sediment during storm runoff. Controlling erosion controls phosphorus.
Nitrate travels with water
It is highly soluble and not retained by soil, so it leaches downward with drainage. Nothing stops it once it is below the root zone.
The legacy problem
Nitrate now arriving in a thick chalk aquifer was applied decades ago. Improving practice today will not show in the borehole for a generation.

Text description

Fertiliser and manure applied to fields reach water three ways. Surface runoff carries phosphorus attached to soil particles into streams within hours of heavy rain. Field drains carry dissolved nitrate to watercourses within days. Leaching carries nitrate down through the soil and unsaturated zone into groundwater, taking years to decades. Each pathway delivers different pollutants on a different timescale.

Hydrionis would like to measure which pages are read, using Google Analytics. It stores an identifier on your device, so we only do it if you agree. Nothing is stored if you decline, and the site works identically either way. See cookies for what is set and how to change your mind.