Follow along with this narrative: Installing conservation practices reduces in-field erosion. Reduced in-field erosion decreases the amount of sediment carried in a stream. Streams carrying less sediment have more energy. Streams with more energy result in additional streambank erosion. Added streambank erosion increases the sediment load in the stream. Ultimately the sediment load carried in the stream remains unchanged. In the end, applying upland conservation only shifts the source of the sediment load from upland erosion to streambank erosion. Logically then, why should farmers install conservation practices if reducing upland erosion doesn’t result in less sediment carried in the stream?
Are you joking? You cannot be serious. The first time I heard this argument I was enraged. I could not imagine the perverted logic that conceived this thought process. What a twisted and warped way to look at the world. It was nothing more than an excuse for farmers.
”Introduce a little anarchy. Upset the established order…”
―The Joker – Heath Ledger
Several years have passed since I heard this argument. Reflecting now, I think the reason I was so outraged is because there is an element of truth in this logic that I did not want to admit. It made me rethink my established order…that any conservation would directly lead to clean water.
Agriculture has significantly changed the hydrology of our landscape. We have replaced forests with cropland. We have plowed under prairie to plant corn and soybeans. We have drained wetlands with tile and drainage ditches. We have straightened streams so they are easier to farm along. All this change in hydrology has reduced infiltration, increased runoff, and amplified the energy in our streams and rivers.
Studies have shown that conservation practices reduce upland erosion, but have led to increased streambank erosion, leaving the total sediment delivery unchanged. Wow, that seems like a waste of time and money.
But doing nothing isn’t the answer. Instead we should do more to modify the current hydrology in a good way. And there are really only three ways we can impact the hydrology enough to reduce runoff and significantly modify stream energy.
1. Replace cropland with permanent vegetation like grasslands and forests.
Permanent vegetation increases water infiltration, thereby reducing runoff. For obvious reasons, it is unlikely that farmers will voluntarily return a significant amount of row crop to permanent vegetation. The Conservation Reserve Program (CRP) has only gotten us so far. But every little bit helps.
2. Increase soil health by using no-till and/or cover crops.
Improved soil health leads to greater infiltration and less runoff. Soil health, in theory, is the best solution. However, soil health is not a permanent fix. Years of improved soil health generated by no-till can be undone in a few short years. For example when a super weed surfaces, like Palmer amaranth has, farmers may believe they need to use more aggressive tillage.
3. Retention structures like ponds and wetlands lessen runoff.
Installing more ponds and wetlands is the most effective and permanent solution to reducing stream energy. Ponds and wetlands even provide lots of secondary benefits. But they are expensive and time-consuming to engineer…up until now.
As I have said in earlier blogs, I don’t believe in silver bullets. In theory, any one of these solutions could succeed. But in reality, implementing only one approach will fail. We should never put all of our eggs in one basket. I suggest we promote all three options and keep our eyes wide open about the limitations of each one. Let’s avoid the twisted logic that concludes any conservation practice, wherever it lands, helps achieve our goal for cleaner water.
We need to support farmers by being honest with them about the benefits, as well as the limitations, of the what and where of conservation practices. Furthermore, we need to be honest about how and where we spend our precious conservation dollars. Doing more is not necessarily better – what I have often referred to as the shotgun approach. We need to be precise in our efforts to modify hydrology, or else all our efforts to reduce soil erosion will fall short of producing cleaner water. That is logical. And we can’t wait.
Voice your opinion. Please add to the dialogue by including your comments below. How do you suggest we introduce a little anarchy into the current strategies guiding what and where conservation practices belong?
Trial and Error Conservation is Expensive
Tom, great observations as always. One other uncomfortable aspect to the logic sequence on sediment in your introduction is the assumption it makes that the source of sediment doesn’t matter if the water contains dirt. While uncomfortable to state, even if the logic is sound and the same amount sediment is contained in the water, it still matters to all of us if that sediment is eroded soil off a field or if it’s from a stream bank. Yes, stream bank erosion may be so dramatic that it too can rob farmland, but the direct loss of soil from production ground into the stream is an escalating harm that is not irrelevant as the source of sediment. Put another way, even if the water is equally impaired with sediment, there is a vital conservation need to keep soil in fields. Which, of course, is a parallel to your ultimate point: Conservation isn’t as simple as single output analysis can make it seem. Just as implementing only one approach will fail, valuing all conservation in support of only one metric (e,g, sediment) also fails.
Keep up the great work.
Brad, I absolutely agree there are enormous benefits to keeping topsoil in the fields. It is ridiculous to think we can ever achieve improved soil health without controlling in-field erosion. However, a little honesty goes a long way. I do not want to sell the public on cleaner water by just changing in-field erosion. If they are paying the bill they need to understand the sediment load may not change. Do you agree?
Spot on, Tom. Really well-meaning people and projects focused on priority practices (important and deserving actions like filter strip or cover crop initiatives), inadvertently lead the public to believe that the problem is that a select practice is not being adopted. If it only were, the public infers, water quality would be “fixed.” But as you point out so well, there is a vast array of interactions in the agricultural landscape, and that requires an array of site-specific responses. Stated a little differently, I sometimes hear the sincerely-made statement relative to water quality: ” we know what works, we just have to do it.” While I believe that can be true given a specific physical site with the availability of the entire tool box of practices and management, the public does need to understand that it is just false to believe that there is a known response to universally resolve the ag water quality challenge but people like you and me are somehow choosing to not do it. The reality of trade-offs and unaligned outcomes in the pursuit of water quality is frustrating, and yes, it is important the public understands that is how it is.
Brad, nicely said.
My thoughts are along the same lines. I say, it is really hard to quantify dollars of soil saved with conservation practices. We can see the erosion at times but it is hard to put a dollar figure on that loss. However, nutrients lost do have an easier quantifiable dollar figure. Nutrient saving can justify added costs to the farm.
excellent story Tom. How can one argue these facts? keep on writting!
Roger, thanks for the encouragement. I enjoy writing about conservation.
4. Good conservation practice means giving up some land adjacent to streams to encourage healthier stream functions: remeander channelized stretches, reslope cut banks to reduce energy, and create low floodplain size at bank toes that slow the stream and permit sediment drop. The answers are here, as well as in the crop ground and adjacent waterways and pastures. Consider that the streams are in a highly damaged condition that’s been building up for around 150-170 years. How do we treat farm ecosystems as systems, not just small chunks to tweak here and there?
Leland, you are correct. Stream stabilization practices are a fourth way to modify hydrology. I should have mentioned this method. I tend to ignore stream stabilization because of the high costs and failure rate. It is easy to point to some successful stream stabilization projects, but certainly there are the failures. When dealing with stream stabilization it is critical to understand the stage of the stream: http://riverrestoration.wikispaces.com/Channel+evolution+model
I will ignore the math of stream energy required to carry sediments and the alternate source theory you described even though it may be supported by science….My advise to farmers and landowners would be make soil conservation a priority to keep their soil on their fields.
I think it is a moot point for acedemia and water pollution regulators to debate if the sediment load would have the same consequence if from rainfall energy from a field or detached by stream energy from the banks or streambed.
Thanks for this introduction to anarchy… or possibly rising to chaos theory…
Dennis, I agree it is critical to control erosion and improve soil health. I just want to have an honest conversation with the public on what they should expect. I am all for funding conservation with public money (see past posts), but I think we need to set clear exceptions on what the public is going to get. If we are not going to improve water quality, then lets say so.
I think we should focus on soil conservation soil health, flood mitigation, etc as reason enough for public funding , and also suggest that it improves edge of field water quality, along with honest discussions about sources of sediments downstream. Your points do widen WQ issues and concerns considerably….
For an in-depth look at the rural stream hydrology issue in the upper Midwest have a look at the on-line booklet titled Fields to Streams: Managing Water in Rural Landscapes (University of Minnesota Extension). You can download it (free) in two pdfs from z.umn.edu/FieldsToStreams
Thanks for the resource, Les. I appreciate your effort to provide this information.
Not certain that the comment passes the smell test. But I’ve read it on the Internet so it must be true.
However, if it was true globally, the Mississippi River delta should be expanding as it has for thousands of years (i.e., since the last glacial retreat) as opposed to shrinking due to a lack of sediment.
Keeping livestock out of streams is known to have a significant impact but similar research on keeping wildlife out of streams has been ignored. Happened to have the opportunity to watch streambank erosion on a section of a HUC 8 river. On year 1, a beaver girdled a tree on the inside corner of a large oxbow loop. In Year 2, the dead tree dropped into the river changing stream flow along the bank, and most of the top broke off and washed away in a flood. In year 3, the next major flood washed out the rootball and subsequently (over a day or so) washed out a 10’ x 10’ x 2000’ section of streambank. Don’t worry, the sediment all got trapped by the Saylorville Reservoir.
The same goes for sediment washed into open tile intakes across the Des Moines Lobe. I know of hard data on sediment loss via this route but I know of no farmer that has ever had to raise an open intake because of sediment disposition in a prairie pothole with an open intake in it. A simple system to force water to pond (i.e., allowing sediment to settle) before being allowed into an open intake would go a long way to resolving sediment loss. Widespread adoption of a microscale hydrology modeling which allowed farmers to visualize sediment movement in their own fields would quickly change attitudes. This is only a 25 year old approach pioneered at UC-Davis.
Interestingly, the technology needed to collect objective streambank and streambed data over time now exists (sidescan LIDAR for streambank documentation and high resolution SONAR for streambed documentation (both operating from a hovercraft) feeding a microscale riverine hydrology model). But for some reason, that opportunity is being ignored.
Tom, I appreciate your comments but without understanding the true balance of sediment in streams, you are making large assumptions that simply aren’t true. A stable stream (obviously one without major perturbations like farming, roads, culverts etc. within it’s watershed) would have a sediment budget that offers both a rate of aggradation and degradation of portions of the system, that are equal. This is the definition of a stable stream channel. A simple reference can be seen here: http://www.fgmorph.com/fg_4_9.php) By reducing the soil loss in the upland portion of a watershed through increased BMP’s, we offer the opportunity for the stream to function more like the natural state. We give the opportunity for vegetation to aid in infiltration, nutrient processing and base flow storage. By offering floodplain access the aggradation that occurs reforms the channel to the hydrologic capacity of the watershed. Increasing vegetative buffer areas builds more stable banks and flood plain areas. So, the BMP’s applied to the landscape DO NOT increase energy in the stream flow and DO NOT degrade banks within the stream channel. The concept is simple, before we modified the landscape, streams functioned very well. We augmented the quantity and quality of sediment and water through what was conventional tillage/farming practices. By reversing these practices, through the use of BMP’s to more like what it was previously, we have everything to gain: more stable base flows, more stable stream banks and more natural discharge and finally, cleaner water.