Tile flow variability

Tile flow variability

UW Discovery Farms has been monitoring the water flow from 24 tile monitoring sites in northeast Wisconsin since October 2017. The goal of this project is to understand how farming practices and management systems influence tile water quality. We are monitoring flow rates and collecting water samples from tile systems to analyze nutrient and soil concentrations. There are three levels of monitoring in this project. Four intensive sites have 24/7 monitoring equipment that continuously measure tile flow rates and automatically take water samples.  Nine sites are intermediate, that continuously monitor flow, but have water samples collected bi-weekly by Discovery Farms staff.  Eleven basic sites have bi-weekly flow measurements and water samples taken at tile outlets by Discovery Farms staff.  Flow data from the intensive sites and bi-weekly tile checks are providing a look at when tiles flow in Northeast Wisconsin.

Huge variability in flow frequency

The biggest surprise so far is the extreme variability in the frequency of tile flows. In the seven months we have monitored, we have seen tiles that flowed only 3 or 4 days, tiles that have only stopped flowing for 3 or 4 days and everything in between.  How often and for how long a tile system flows is extremely site specific. For example, there are two sites in Manitowoc County a half mile apart from each other. One site has flowed every day, and the other has only flowed a handful of times after heavy spring rains.  We have not observed a relationship between frequency of tile flows and the tile system size or density. It comes down to the site conditions including; What kind of soils are tiled?  Is there a perched or high water table?  What is the field slope? How much precipitation has the field received? All these conditions, and many more, play a role in how often a tile system will flow.

Frequency of checks

This project has reaffirmed the value of having 24/7 monitoring to collect water data. Without having continuous monitoring, valuable information might be missed. The Shawano County intensive site is an excellent example.  We take a water sample and flow measurement at the intensive sites during the bi-weekly tile checks. The Shawano County intensive site has only had water flowing through it twice during a bi-weekly check, both in the spring. If those bi-weekly checks were all the data we had, we would say that this tile system only flows in the spring. However, the constant flow monitoring equipment tells a different story. This tile system has flowed for short periods throughout the winter and spring. It is only during late April and into May that it has flowed consistently enough for us to witness. Continuous flow data provides a more accurate picture of flow patterns.

Frozen tiles

Another interesting find has been the variability of tiles freezing during winter.  We had a fiercely cold winter, but even during more typical stretches of winter weather, multiple tile systems froze at the outlet. One tile was frozen for 10 weeks straight, while others flowed straight through the winter.  Tile systems than run constantly tended not to freeze solid, while tiles that flow on and off were more likely to freeze.

The big takeaway is that there is extreme variability in how often and for how long a tile system will flow. Even on the same farm, and even the same field, tile systems will behave differently.  Get to know the tendencies of the tile systems on your farms, as this is important information to consider when managing your fields.

Stay tuned for more information from the first year of the tile project coming this winter. §