The Effect of Stream Channel Incision on Groundwater Depth in Riparian Corridors

By: Doug Gass | South Skunk River Watershed Project Coordinator

Hilary Pierce presented on the effect of stream channel incision on groundwater depths for Iowa Learning Farms April 1 webinar.

Image Credit: USDA National Agroforestry Center

Groundwater levels in riparian corridors can have a significant impact on nitrate removal. High groundwater levels keep soil saturated and create anaerobic conditions allowing for denitrification to occur. As streams incise deeper into the ground, they leave their banks less often and spend less time in the flood plain, which could create lower groundwater levels along the riparian corridors. For her masters degree research at the University of Minnesota, Hilary observed how stream incision impacted the depth of groundwater in these corridors.

Six sites were studied in southern Minnesota throughout the Minnesota River valley. The level of stream incision was classified for each site, along with a variety of other characteristics, including soil type, vegetation type, watershed area, and local groundwater discharge. Hilary and her collaborators then recorded how often the groundwater in these sites rose to within 50 centimeters of the ground surface.

This research found a significant relationship between streambed depth and groundwater levels, with more deeply incised streams having lower groundwater levels. Hilary also found that other factors had more significant impacts on groundwater levels in riparian corridors, with stream stage and local groundwater dynamics being the most influential factors.

In the future, Hilary wants this type of research to be expanded to include more sites in a wider geographic area. She is also doing regression analyses for predicting riparian groundwater levels. It is her hope that local factors such as precipitation, evapotranspiration, and stream stage can be used to create a model for predicting riparian groundwater levels at any site.

Watch the full webinar here. We also have many other great archived webinars available here: https://www.iowalearningfarms.org/page/webinars.

Join us next week, on April 8th at noon, for the webinar “Succeeding with Cover Crops & No-Till: A Guide for Spring 2020” presented by Liz Ripley & Mark Licht.

April 1 Webinar: Stream Channel Incision & Groundwater Depth in Riparian Corridors

Iowa Learning Farms will host a webinar on Wednesday, April 1 at noon. This webinar will explore the relationship between stream channel incision and the depth to groundwater in riparian corridors.

Riparian vegetated buffers have the capacity to remove nitrogen from shallow groundwater in the riparian corridors, but this function depends on the denitrification potential of these areas. The highest potential for denitrification will occur in areas with available organic carbon and high levels of nitrate, where there is also saturation of the riparian zone near the ground surface. Interactions between the shallow groundwater table and riparian vegetation will also remove nitrogen from groundwater through plant uptake.

By determining the relationship of precipitation, evapotranspiration, stream stage and soil characteristics to the groundwater depth in the riparian corridor, it may be possible to better guide vegetated buffer planning. This could maximize buffer efficiency in areas where it is not possible to monitor groundwater depth. Streams with a higher degree of incision may be less likely to have elevated groundwater tables, reducing their potential for nitrate removal from shallow groundwater.

Hilary Pierce, an Extension Outreach Specialist with Iowa State University, will discuss this research project, which analyzed six sites in southwestern Minnesota.

A Certified Crop Adviser board-approved continuing education unit (1 CEU) is available for those who are able to participate in the live webinar. Information about how to apply to receive the credit will be provided at the end of the live webinar.

Don’t miss this webinar!

DATE: Wednesday, April 1, 2020

TIME: 12:00 pm

HOW TO PARTICIPATE: shortly before 12:00 pm on April 1st:

Click this URL, or type this web address into your internet browser: https://iastate.zoom.us/j/364284172

Or, go to https://iastate.zoom.us/join and enter meeting ID: 364 284 172 

Or, join from a dial-in phone line:

Dial: +1 312 626 6799 or +1 646 876 9923

Meeting ID: 364 284 172

The webinar will also be recorded and archived on the ILF website, so that it can be watched at any time. Archived webinars are available at https://www.iowalearningfarms.org/page/webinars.

Hilary Pierce

Watershed Scale, Not Field Scale

If we hope to significantly improve water quality in Iowa and still farm profitably, we are going to need to change our mindset about our agricultural systems. We are going to need to start thinking in terms of watersheds.

Each spring I teach a graduate course for the Iowa State University Master of Science in Agronomy distance program called “Agronomic Systems Analysis.” The course is comprised of field-scale case studies that require students to consider how complex decisions must be made by taking into consideration agronomic, economic, environmental, and social implications of the decisions. This year, I incorporated a new lesson that goes beyond field scale but encourages the students to address the issues at the watershed scale.

shelbyemphemeral-e1506974374896The point of this lesson is to have students think not about a single farm or field but to think about where to target practices to be the most effective. And which practices will draw the most reduction of nutrients being lost. This is not rocket science. It has been well established that sloping land is prone to erosion. These are the areas where no-tillage and cover crops are going to be the most effective at keeping soil and phosphorus in place. It’s well understood that well drained soils with very little slope are prone to nitrate leaching. These are the areas where bioreactors, wetlands and cover crops will be most effective in reducing nitrate movement into flowing water.

For several years, the Iowa Learning Farms and Iowa State University Extension and Outreach have been talking about implementing conservation practices and the scale of conservation practice adoption that must occur to reach nutrient reduction goals. For instance, one scenario calls for statewide adoption of MRTN (maximum return to nitrogen) rates along with 12 million acres of cover crops, 12 million acres of no-tillage, 6 million acres treated by bioreactors, and 7.5 million acres treated by wetlands. That effort to date has achieved approximately 625,000 acres of cover crops, 5 million acres of no-tillage, 950 acres treated by bioreactors and 42,200 acres treated by wetlands. We have a long way to go.

Cover crops

Reaching conservation practice goals will take everyone thinking about how his or her footprint impacts the watershed as a whole. It will take targeting practices for maximum effectiveness with minimal impact to the cost of production. Wetlands can be installed to treat water flowing from multiple fields. Prairie strips in strategic locations can minimize sediment and phosphorus loss. Saturated and riparian buffers will reduce nutrient movement and streambank sloughing of rivers and streams. It can even be as simple as installing a waterway to connect waterways from adjacent fields or no-tilling soybean into corn residue.

There can be watershed and community benefits that extend beyond the fence. Many practices can support efforts to provide habitat for pollinators, monarchs, song birds, game birds, waterfowl and deer.

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We cannot meet the Iowa Nutrient Reduction Strategy goals and improve habitat without changing our mindset about how we farm and the use of conservation. Conservation practices are most effective if they are targeted specifically in areas that will result in a continuous, complimentary system across the watershed.

How can we help you think on a watershed scale?

Mark Licht

Mark Licht is an Iowa Learning Farms team member and Assistant Professor and Extension Cropping Systems Specialist at Iowa State University.

Raining Cats and Dogs

Earlier this summer, I shared a Dog Blog in which J-Dog and I explored the stream bank restoration and watershed improvement work done along College Creek here in Ames.

On Saturday night into Sunday morning, we were hit with a healthy dose of rain: 4.20” reported by the National Weather Service, with amounts upwards of 6” reported locally. Join us on another walk to see how the College Creek restoration efforts are holding up when really put to the test.

Conservation Dog Jackie checking out the creek as the waters rise

Conservation Dog Jackie checking out the creek as the waters rise

What is usually a quiet stream practically narrow enough to walk over in places, College Creek turns into a fast-moving, churning stream after a 4+ inch rain.

Usually a quiet stream practically narrow enough to walk over in places, College Creek turns into a fast-moving, churning stream after a 4+ inch rain.

As part of the restoration efforts, a combination of trees, shrubs, native grasses, and forbs are being used to protect College Creek from sediment and nutrient loads from the surrounding watershed.

The riparian buffer appears to be doing its job well!  While the force of the moving water has laid down many of the grasses along the stream’s edge, this dense vegetation is providing ground cover and protection from erosion along the stream banks.

The riparian buffer appears to be doing its job well! While the force of the moving water has laid down many of the grasses along the stream’s edge, this dense vegetation is providing ground cover and protection from erosion along the stream banks.

In addition to bank stabilization, these buffers also add great beauty to the neighborhood.

College Creek’s riparian buffers include trees, shrubs, native grasses, and forbs. Native vegetation, such as the grayhead coneflower shown above, also supports healthy populations of pollinators!

College Creek’s riparian buffers include trees, shrubs, native grasses, and forbs. Native plants, such as the grayhead coneflower shown above, also support healthy populations of pollinators!

One happy husky, even during the dog days of summer…

One happy husky, lovin’ the dog days of summer…

While I don’t have any photographs to document it, the neatest part of the walk was an up-close-and-personal encounter with a great blue heron, fishing right along the edge of College Creek, just minutes from my door.

The husky wanted to befriend the heron much more than the heron cared to meet the husky.  This prompted the heron to quickly take off in flight – so graceful, and at the same time, so awkward – quite the moment to experience.

Ann Staudt

Dog Blog: Scoping out urban conservation practices

Join J-Dog and me on our walk as we take a look at several urban conservation practices happening in the neighborhood!

Leashed up, ready to rock and roll!

Last week, I shared my #1newthingforwater for 2015 – working with my HOA to repair several areas on the property that have experienced significant amounts of erosion, and working to get new vegetation established there. Let’s take a look at where things are at now…

We're starting to get some growth here on this slope

We’re starting to get some nice growth here –  this slope used to be completely barren!

Close-up shot

Close-up shot of new grass establishment

 

We have many different walking routes through the neighborhood, but one of our favorites runs along College Creek.  Iowa State University and the City of Ames partnered on the College Creek Restoration Project several years back (read more on the City of Ames Smart Watersheds page – you’ll have to scroll down a bit to get there).  Take a look at College Creek today!

A combination of trees, shrubs,

A combination of trees, shrubs, native grasses, and forbs are being used to protect College Creek from sediment and nutrient loads from the surrounding area.  In addition to stream bank stabilization, these buffers also add great beauty to the neighborhood.

 

Five adjacent homeowners agreed to participate in a

Five adjacent homeowners agreed to participate in a stormwater garden research/demonstration project with Iowa State University and the City of Ames.  Established in 2008, these backyard gardens help to intercept and slow the flow of water that would otherwise run directly into College Creek.

Time for a little break… as the song says, Everybody Poops!

DSCN9442

“Dogs are poopin’ on their walks; geese are poopin’ at the beach.  All these things impact our water, that’s the reason for this speech!” – Lyrics from Everybody Poops

 

 

Scoop the poop

Scoop the poop! Did you know… 1 gram of dog waste contains 23 million fecal bacteria!

OK, time to finish up the walk…  we’ll leave you with one final view of the College Creek restoration project.

Very

Very tempting to go for a little swim!

A beautiful walk on a beautiful evening… thanks for joining us.

Ann Staudt