LNWB Ch09 Artificial Drainage

Overview:
Artificial drainage is used throughout WRIA 1 to aid in the flow of water on top of or through the soil, sometimes to slow it down, other times to direct it to a specific location at any given depth of the landscape. Some of these systems are critical to the farm operations that make Whatcom County one of Washington’s top agricultural producers, others help riverside and lowland communities alleviate the impacts of high flowing rivers and streams. In high precipitation events, increased numbers of flow pathways provided by artificial drains may increase the peak stormwater quantities and contribute to flood impacts. Some artificial drains may even offer opportunities to improve low instream flows in the late season.

Purpose:
The model feature that represents artificial drainage has been incorporated into WRIA 1 Topnet Water Management (Topnet-WM) because of the assumption that agricultural drainage installed during development of agriculture in WRIA 1 has altered the runoff processes to a large enough degree that these alterations should be part of the simulation. Calculating how the ditches and tiles influence the drainage of the soils was done based on a drainage coefficient from NRCS technical guides. The Lower Nooksack Water Budget project team used previously existing (2007 Topnet-WM model) compiled information, data and maps of the many ditches and tile drains that exist in the Lower Nooksack study area in order to develop the artificial drainage inputs for the 2012 work conducted on the Lower Nooksack Water Budget.

This resource is a subset of the Lower Nooksack Water Budget (LNWB) Collection Resource.