Amending the Clean Water Act

by Dan Haug | Aug 28, 2025

When the House of Representatives reconvenes in September, they will likely vote on a collection of amendments to the Clean Water Act: H.R. 3898, which they’re calling the PERMIT Act (Promoting Efficient Review for Modern Infrastructure Today). It’s a bad bill and you should urge your representatives to vote against it.

The Clean Water Act no longer works well in Iowa, because our largest remaining source of pollution is agricultural stormwater runoff, which has a special exemption. The Iowa Department of Natural Resources has been reluctant to put waters on the impaired list and write cleanup plans because they can’t enforce them. They have been reluctant to update standards because they think it will result in higher costs for small town sewage treatment plants without making any noticeable difference for water quality in rivers. I have a whole presentation about impaired waters if you’d like more details, but that’s the situation in a nutshell.

HR 3898 makes this worse. It expands exemptions for agricultural stormwater and pesticides without any provisions to encourage conservation. It mixes economic considerations into the process for setting standards and evaluating impairments. If there’s no widely available and cost-effective way to get a pollutant down to the level that science says is needed to protect aquatic life or drinking water, then the DNR would have to set a weaker standard, or delay setting standards. This would leave the public in the dark about the condition of our lakes and rivers.

Oxbow wetlands have lost protection because do not have a "relatively permanent" surface water connection to a navigable water.

How often does a stream need flowing water to be protected?

There has been a long-running controversy over the extent to which the US Army Corps of Engineers and EPA can regulate construction in wetlands and waterways, which hinges on the definition of phrase: “Waters of the United States.” The Supreme Court recently ruled that many kinds of wetlands aren’t covered. This bill would exclude ephemeral streams, which had previously been considered on a case-by-case basis. I would be less worried about the impacts of these decisions if Iowa had state law requiring developers to avoid or mitigate wetland fill, like some of our neighbors do.

HR 3898 goes beyond clarifying a few exceptions to roll back what many people see as federal overreach. It also raises the threshold for general permits, making it easier to fill small wetlands even if they do have an obvious connection to navigable waters. It makes it harder for states to block pipeline projects. Amendments by Democrats to study the impacts of the bill or mitigate them with a no-net-loss policy were rejected and the bill passed out of committee on a party line vote.

The Cuyohoga River in Ohio caught fire nine times before Congress took serious action to address water pollution

The one good thing about the bill is it’s a reminder that Congress does have the ability to fix outdated laws. What we now call the Clean Water Act are the 1972 and 1977 amendments to the 1948 Federal Water Pollution Control Act. Those amendments made a big difference for waters that were once polluted by sewage and industrial waste. This summer, I paddled on a beautiful and relatively clean stretch of the Shell Rock River with a canoe partner who grew up in the area and recalled how foam used to float down the river from meatpacking plants in Minnesota. The law was amended again in 1981, 1987, and 2014. It could use another amendment to cut red tape while better addressing today’s water quality challenges, but this isn’t it!

How I Spent My Summer Glaciation

by Dan Haug | Aug 25, 2025

If I was in elementary school, this is what my back-to-school essay would look like.

I’m sharing some vacation photos, taken at the Athabasca Glacier in Alberta, Canada, because it’s a nice window into Iowa’s icy past and its warming future. Earth science concepts like glacial moraines and watersheds and climate change that can be subtle or hidden in Iowa are plain to see in the mountains!

1. Glacial Ice

This is the Athabasca Glacier. It’s a slow moving river of ice 4 miles long and 300-980 feet thick, sliding off the larger Columbia Icefield in the Canadian Rockies. It looks big from a distance, and it feels even bigger when you’re walking across it on crampons and aren’t used to the altitude! The depth of the ice became apparent when we looked into a crevasse.

All of Iowa looked like this at some point during the last 2 million years, except the ice was even thicker. The Des Moines Lobe of the Wisconsinian ice sheet melted from northern and central Iowa just 12,000 years ago, leaving behind flat, marshy land. Other parts of Iowa have been ice-free for longer and had more time for wind and water to shape the hills and valleys.

Ground moraine and a lateral moraine deposited by the Athabasca glacial

2. Glacial Till

A sheet of ice hundreds of feet deep is heavy, and pushes against the earth with tremendous force as it slides slowly downhill. This photo shows both the scratches on the bedrock made by the glacier and the glacial till that it leaves behind–an unsorted mix of sand, silt, gravel, and boulders. You don’t have to travel to the Canadian Rockies to see Canadian rocks; during the ice age, the glaciers carried some all the way to Iowa!

Like a bulldozer, glaciers smooth out the ground underneath and leave a big pile of material at the edge when they stop. That’s why there’s a line of hills near Des Moines and a lot of flat land north of there. You can see a flat ground moraine in the foreground of this picture and a steep lateral moraine in the background.

Purple saxifrage flowering at the edge of a glacier

3. Soil Formation

Despite the harsh conditions at the edge of the glacier, a few tiny flowers were blooming! This plant is a Saxifrage, “stone-breaker” in Latin. Plant roots and associated fungi speed up the process of breaking down rock and turning it into soil.

It’s still a slow process! It took thousands of years for prairie roots, microbes, and burrowing animals to turn lifeless glacial till into Iowa’s rich black topsoil, but only 160 years of tillage to lose half of it. Fortunately, there are ways to grow crops without degrading our soil. As Practical Farmers of Iowa puts it, “don’t farm naked!”

Aerial photo showing continental divide at Columbia Icefield

4. Continental Divide

The Columbia Icefield sits at the junction of two continental divides. Meltwater from the Athabasca Glacier joins the Saskatchewan River, which ultimately makes its way to Hudson Bay. However, meltwater from the Stutfield Glacier on the other side of the mountain ends up in the Arctic Ocean, and meltwater from the Columbia Glacier goes to the Pacific Ocean.

In the Canadian Rockies, the watershed boundaries are impossible to miss: lines of awe-inspiring mountain peaks on either side of a river valley. You might be driving along the Bow River until you reach it’s headwaters, and then you come to a mountain pass, your ears pop, and… ta da! You’re in a new watershed, following the Mistaya River downhill.

In Iowa, the dividing lines between land that drains to the Mississippi River and the Missouri River (or any other pair of rivers) are hard to find without a topographic map. We’ve put up watershed signs around Story County to make it more obvious.

Why does is matter what watershed you’re in? Well, knowing which land drains to which river can tell you something about the water quality in the river, and who to talk to if you want to improve it.

Fine silt in glacier meltwater makes for beautiful blues and greens

5. Meltwater

Our guide refilled our water bottles from a stream of glacial meltwater. I felt comfortable drinking it without boiling or filtration because nothing lives on a glacier. Elsewhere in the mountains, there’s a risk that wild animals living in or near the water might have left behind a little present containing a parasite like Giardia. Fecal contamination tends to get worse as you move downstream into areas with a lot of cows or a lot of people, and Alberta has its own set of water quality issues associated with mining and oil extraction. However, there’s a notable difference from Iowa: when natural resource agencies issue a beach advisory because of E. coli, it’s unusual enough to make the news!

Lakes can be bluish green from minerals or from algae

The water from the glacier was refreshing but tasted a little… dusty. Like the taste in your mouth when you’re standing on a gravel road and truck passes by. Ames tap water is better!

However, the glacial dust (rock flour) reflects the light, turning mountain lakes a lovely shade of blue, turquoise, or green. In Iowa, green or blue-green colored water is usually a sign of an algae bloom, unpleasant to swim in and possibly toxic!

Changes in the Athabasca Glacier from 1917 to 2011

6. Climate Change

We made sure to include a visit to the glacier in our vacation plans because there may not be many more opportunities to see one. In a stable climate, a glacier would melt a bit in summer and grow back with winter snows. In a warming world, glaciers are melting rapidly.

Driving from the visitor center to the trailhead, we passed a series of ridges (terminal moraines) marked with dates. Since 1844, the ice has been receding and the pace of melting has accelerated in recent years. None of my pictures capture this, so I will screenshot an a pair of images from the Mountain Legacy Project and point you to Amy Snider for more art, maps, and photos about the Athabasca Glacier.

Climate change has been less noticeable in Iowa than in other parts of North America because of the moderating influence of corn sweat (evapotranspiration), but that won’t last. Rising temperatures, more intense spring rains, and greater weather variability are projected to lower yields and undermine what little progress we’ve made in addressing water quality. Alberta’s economy is dependent on fossil fuels, but Iowa has a lot of gain from a transition to green energy, and a lot to lose if we don’t make the switch.

Trilobite fossil in a rock dislodged by the Athabasca Glacier

7. Fossils

At the edge of the glacier, we saw a trilobite fossil in a 510-million year old rock, a relic of a time when erosion rates were even higher than they are now because there weren’t any plants yet. The broken shells, sand, and silt that covered the seafloor has since turned to rock and been pushed up to form new mountains.

The trilobites are long gone, wiped out during another episode of global warming and ocean acidification, this one triggered by massive volcanic eruptions 252 million years ago. It was the biggest mass extinction in Earth’s history, but after fifty million years or so, the land, seas and sky were teeming with new species.

If you take a long enough view, arable soil, clean water, and biodiversity are renewable resources. On human timescales, they’re definitely not. Agriculture and civilizations developed during a time of stable climate, and they may not last much longer if we don’t take more aggressive action to limit greenhouse gas emissions. The Earth will go on without us.

My Geology Summer Reading List

Landforms of Iowa, by Jean C. Prior

Timefulness by Marcia Bjornerud

Otherlands by Thomas Halliday

Progress Tracking: Why It’s Lacking

by Dan Haug | Jul 31, 2025

If the Iowa Nutrient Reduction Strategy had a United Way style progress banner

You know those United Way posters with a thermometer showing progress toward a fundraising goal? The image above is my attempt at a similarly easy-to-understand progress meter for the Iowa Nutrient Reduction Strategy (INRS). Based on changes to farming practices in the decade since the Iowa Nutrient Reduction Strategy was released, we should have met our goal for phosphorus but have only reduced nitrogen losses by 2%, not enough to undo the increases of the previous decade. These are best-case scenarios which do not account for manure, legacy sediment and nutrients, and interactions between practices.

Iowa State University is responsible for tracking the progress of the INRS, and has created a set of data dashboards covering dollars spent, minds changed, conservation practices on the land, and water quality trends in the rivers. These were updated in May of 2024. There is no top-line summary of where we stand relative to our goals, but wasn’t hard to make one. I just added up the numbers in a pair of tables labelled “change in modeled nitrogen/phosphorus load for practices since the baseline period.”

Change in modeled nutrient loads, from ISU dashboard

Baselines, Goals and Timelines

The timeline requires some explanation. The INRS was released in 2013, but the baseline period is 1980-1996. That’s because the Hypoxia Action Task Force was formed in 1997. The task force set a goal of reducing the size of the dead zone in Gulf to 5000 square kilometers (1,930 square miles). The target date for meeting that goal has been pushed back several times. Despite several dry years, the five-year average extent of the dead zone is still twice as big as the target. Last year it measured 6,705 square miles, larger than Connecticut or Hawaii.

To meet the goals for shrinking the dead zone, each state would need to reduce the amount of nitrogen and phosphorus lost down the Mississippi River by 45%. The Iowa Department of Natural Resources determined that mandatory upgrades for 102 municipal wastewater treatment systems and 28 industrial facilities could reduce state’s overall nitrogen load by 4% and phosphorus load by 16%. The remaining 41% reduction in nitrogen load and 29% reduction in phosphorus load would need to come from controlling non-point sources of pollution like agricultural runoff.

Iowa State University was tasked with answering the question: “based on what we know about the performance of various conservation practices, how would it be possible to achieve these goals?” The answer was “only with a combination of practices, and only if every farm uses at least one of them.” This research began in 2010, using data about land use and farming practices from the previous five years (2006-2010), so the load reduction scenarios are relative to that “benchmark” period. The researchers later issued a supplemental report to compare the benchmark period to the baseline. Phosphorus went down due to changes in tillage but nitrogen went up due to an increase in corn and soybean acres and an increase in fertilizer application rates.

Using the information in ISU’s reports and dashboards, I’ve attempted to summarize our progress relative to both the baseline period (before the formation of the Hypoxia Action Task Force) and the benchmark period (before work began on the Iowa Nutrient Reduction Strategy).

Table showing progress of INRS relative to two periods

Modeling vs. Monitoring

As I said, these are best-case scenarios. While we can certainly expect a big reduction in phosphorus pollution from the growth of no-till and cover crops, ultimately, the only way to be sure that water quality is improving in our rivers is to test it! If there’s a discrepancy between what you expect (a big reduction in phosphorus load) and what you measure (no clear trend in flow-weighted, five-year-moving-average phosphorus loads) that’s a sign that you left something important out of the spreadsheet! The most likely suspects are legacy sediment in the river valleys and livestock manure.

On the other hand, if your water quality data is incomplete or inconclusive or just hard to explain, it’s worth stepping back and asking yourself: “how big a reduction in nitrogen can I reasonably expect, based on the conservation practices installed so far?” If the answer is “1 or 2 percent,” there’s no need to wait for the results of a long-term study to acknowledge that your strategy isn’t working.

I remember doing that kind of reality check in 2019 for the Ioway Creek Watershed Management Authority, at the end of a four-year demonstration project. I did not enjoy being the bearer of bad news then, and I’m not enjoying it now. I remember how much work my colleagues put into those field days, and the ingenuity and vision displayed by the farmers who hosted them. I was there when the woodchips were poured into the first bioreactor in Boone County. So I totally understand the impulse to brag that Iowa now has 300 bioreactors, 3.8 million acres of cover crops, and 10.2 million acres of no-till. Many people worked hard to achieve those numbers! It is real progress! It’s kept nutrients and sediment out the water! It proves that there are many farmers who care about soil and water and are doing something about it! But it doesn’t prove that the Iowa Nutrient Reduction Strategy is working. For nitrogen, it definitely isn’t.

A field day in 2017 for the Ioway (Squaw) Creek Watershed Project

Conservation efforts have been partially offset by increased fertilizer use

I knew that we needed a lot more cover crops, wetlands, and saturated buffers to reach our nitrogen goal. Iowa Environmental Council has made this point with infographics. What I didn’t realize was the extent to which increases in fertilizer application rates have offset the hard-won gains that we’ve achieved so far.

Nutrient rate management was supposed to be the low-hanging fruit the Iowa Nutrient Reduction Strategy. At the time the INRS was written, the Maximum Return to Nitrogen (the point at which the yield bump from an additional pound of fertilizer doesn’t generate enough revenue to cover the costs) was 133 lbs/acre for corn in rotation and 190 lbs/acre for continuous corn. Reducing rates from 150 lbs/acre for corn in rotation and 201 lbs/acre seemed like an easy way to reduce nitrogen in the rivers by 10% while actually saving farmers money. Win-win! Instead, rates for corn in rotation averaged 173 pounds/acre for the past several years, which would raise nitrate levels in tile water by (roughly) 23%! Rates for continuous corn went down just a tiny bit, to 199 lbs/acre. What happened?

Expected response to nitrate in tile water based on fertilizer application rate

Several of the authors of the INRS science assessment just co-authored a new paper in Nature Communications which provides an answer. 133 lbs/acre was economically optimal under outdated assumptions about corn genetics and yield response, fertilizer and corn prices, and precipitation. Factoring all that in, the optimal rate for corn in rotation actually rose to 187 pounds/acre in 2020, leaving no opportunity for a win-win. Farmers are acting in their rational economic self-interest and applying as much nitrogen as is required to get good crop yields after a heavy spring rain. (Huge caveat: this doesn’t factor in manure). The researchers acknowledged that this is bad for water quality, as measured by a growing gap between the economically optimal rate and an “environmentally optimal rate” with some externalities priced in. Another way to say that: the fraction of agribusiness profits which come at the expense of other industries (i.e. commercial fishing in the Gulf, tourism for communities on polluted lakes) and the public (i.e. utility bills for customers of the Des Moines Waterworks, hospital bills for cancer patients) has been growing.

The companion piece to this paper is a new calculator. N-FACT uses data from on-farm nitrogen rate trials to factor in location, planting date, residual soil nitrogen, fertilizer price, and your best guess about corn prices and rainfall to provide a customized economically optimal nitrogen rate. The research that went into it is very impressive, and gave me a new appreciation all the factors that can influence agronomists’ recommendations and farmers’ decisions. I hope it will lead to reduced nitrogen losses by helping farmers improve their forecasting, but unless you’re doing a split application and soil or corn stalk testing, it seems like there’s still a lot uncertainty. Your optimal rate may vary by 40 pounds/acre depending on whether we get a wet spring or a dry spring. That’s why I’m more excited about Practical Farmers of Iowa N Rate Protection Program, which directly addresses uncertainty and risk.

What we really need is a calculator to answer the following questions about the Iowa Nutrient Reduction Strategy:

How much voluntary conservation will it take to offset future profit-driven changes in the industry?
How soon can we expect to see meaningful reductions in nitrate in our rivers and drinking water?
How many people will get preventable cancers in the meantime?
How long is the public going to put up with this before we demand a change in strategy?

What do I mean by “a change in strategy?” Making policy recommendations isn’t our wheelhouse, but if you’re looking for ideas, you might start with this 2020 op-ed by Matt Liebman, Silvia Secchi, Chris Jones, and Neil Hamilton, or this 2022 report by the Iowa Environmental Council.

(Don’t) Blame it on the Rain

by Dan Haug | Jul 10, 2025

Gov. Reynolds' interview reminds me of a Milli Vanilli single

Updated on July 31

In an interview with KCCI, Iowa Governor Kim Reynolds blamed the weather for high nitrate levels in the Raccoon and Des Moines rivers that led to an unprecedented outdoor watering ban for the Des Moines metro and dismissed any suggestion that Iowa needs to change its policies. Milli Vanilli’s 1989 hit “Blame it on the Rain” captures the vibe perfectly, so I covered the song and made a silly video with footage from the interview. However, the situation is no laughing matter.

Let me explain the situation as simply and clearly as I can. The high nitrate levels we are seeing this spring are not a fluke, drinking water is not completely safe in many communities across Iowa, and if we stay the course with Iowa’s Nutrient Reduction Strategy we will be waiting a long time for things to get better.

You can’t have it both ways

It’s true, nitrate pollution in rivers is influenced by both rainfall and recent drought. This has been a recurring theme in my analysis of water quality data (most recently here, and most rigorously here). But the Governor and her administration want to have it both ways. When nitrate in the Cedar River dropped due to favorable weather, they took that as a sign that a voluntary approach was working and took the unusual step of trying to withdraw a pollution budget that might have placed limits on new pollution from industry. Just last fall they were arguing that the following rivers should be removed from the Impaired Waters List, based on a 10% rule that makes no sense in the context of drinking water. The table below shows the data that they’re using to make those determinations.

Nitrate data for impaired waters disputed by EPA and DNR

Regardless of whether they meet the technical threshold for impairment, as a practical matter, the Raccoon River and Des Moines River regularly have nitrate levels high enough to cause problems for drinking water supply. The Central Iowa Water Works had to run their nitrate removal facility in 2024, 2022, 2019, 2018, 2017, 2016, 2015, 2014, and 2013. (This was reported recently by KCCI). It’s the largest such facility in the world, and this year it wasn’t enough!

Nitrate levels this spring are higher than average but not a fluke

The graphs below shows how daily nitrate concentrations and discharge (streamflow) in the Raccoon River this year compares to the median for that time of year. It is unusual for wet weather and high nitrate levels to persist through late July, but nitrate does exceed 10 mg/L about half the time in May and June. If you want to understand long-term nitrate trends in the Des Moines River and Raccoon River, read Chapter 5 of the new source water report commissioned by Polk County.

The Raccoon and Des Moines Rivers are not alone in having high nitrate levels this year. Here is 22 years of weekly data from a site on the South Skunk River, just downstream of Ames. This spring, peak nitrate levels (22 mg/L) were the highest we’ve seen since 2014. Average spring nitrate levels (15.5 mg/L) were the highest we’ve seen since 2015. However, it’s only a little above the long-term average (13 mg/L, indicated with a dotted black line) and ranks 7th out of 23 years for which we have data.

Spring nitrate in the South Skunk River, 2003-2025

None of the data I’ve seen rules out a slight improvement in water quality in this or other Iowa rivers, masked by the ups and downs of an 8-10 year cycle. However the data does rule out this year being a fluke and us not having to worry about high nitrate levels in the future!

In Iowa, it’s normal for it to rain a lot in the spring. In watersheds with a lot of tile-drained farmland, it’s normal to see high nitrate levels for several days following a rainstorm. Ames is lucky to have a buried sand-and-gravel aquifer with the right geology and chemistry to remove most of the nitrogen before it reaches wells. If we withdrew water directly from the Skunk River, it would exceed the drinking water standard every year. Many other communities in Iowa are not as fortunate in their geology.

Nitrate in Drinking Water Poses a Widespread Health Risk

The Safe Drinking Water Act was written so that we must draw a hard line between “safe” and “unsafe.” Drinking water utilities must meet a Maximum Contaminant Limit of 10 mg/L nitrate as nitrogen. Most large water systems have been able to say on the “safe” side of the line, although it can be costly to do so. However, the standard hasn’t been updated to reflect research on the link between chronic exposure to nitrate in drinking water and various cancers. And really, it’s better to think of health risks as a continuum from “more safe” to “less safe.” The Environmental Working Group created a map a few years ago showing which communities fall in the “not as safe as they could be” range for nitrate in drinking water. Last year, Iowa Environmental Council recently released a report about the health risks of nitrate in drinking water and is now hosting a series of listening sessions on cancer and the environment.

Conservation efforts have been partially offset by increased fertilizer use

Shouldn’t we expect some improvement in nitrogen levels due to the state’s nutrient reduction strategy and the conservation efforts of farmers? I’ve written another article to dig into this question but the short answer is that we can expect at most a 2% reduction in nitrogen losses over the past decade. That’s for the state as a whole, some watersheds are doing better or worse and we don’t have a good tracking system to evaluate it. Most of the progress that we can expect from cover crops and nitrification inhibitors have been offset by increases in fertilizer application rates, which apparently made economic sense to do.

I can’t really blame farmers for acting in their economic self-interest. I do think it’s fair to blame your elected officials if they can’t take drinking water safety seriously and offer better solutions. Just don’t blame it on the rain.

A Good Day for Volunteerism, A Bad Day For Water Quality

by Dan Haug | Jun 30, 2025

Testing multiple sites within a short time period can provide a “snapshot” of water quality across a watershed, county, or state.

Polk County Conservation had great turnout for their spring water quality snapshot on May 20, testing 117 sites! I scheduled our event for the same day and volunteers help me test another 45 sites in Story, Boone and Hamilton counties. We also did some follow-up testing on May 21 for quality control and collected water samples for the lab. I have assembled the results from both events into a colorful interactive map that shows where water quality was good, fair, or poor in central Iowa during those two days.

There were a lot of “poor” readings on May 20. Not only was nitrate in the Skunk River and Raccoon River higher than we’ve seen in a decade, the water in most creeks was chocolate brown with sediment and had E. coli counts in the thousands.

An Ames High student tests water clarity in Ioway Creek

Ames High students test water quality in Ioway Creek

One reason we do snapshot events is to get a better sense for where that pollution is (and isn’t) coming from. You’ll notice that streams with urban watersheds like Yeader Creek in Des Moines and College Creek in Ames have much lower nitrate than streams in rural areas. However, urban streams had high levels of sediment and fecal bacteria.

The other reason we do snapshot events is to provide a hands-on educational experience for people who might be curious about water quality but who can’t commit to monitoring a stream twice a month. I joined six classes of earth science students (taught by Kean Roberts and Collin Reichert) to test sites within walking distance of Ames High School. While there were a few complaints about the weather and walking in heavy waders, most students enjoyed the break from the classroom and spotting wildlife. The data students collected is part of a larger citizen science effort.

Ames High students test chloride in a tributary of Ioway Creek

Ames High student tests water clarity in a tributary of Ioway Creek.

Volunteers in the Ioway Creek watershed have been doing twice-a-year snapshot events since 2006. Prairie Rivers of Iowa helped keep the tradition going after the IOWATER database was shut down in 2017, and we are in the process of uploading the data from those events to a permanent home on the Izaak Walton League’s Clean Water Hub!

However, I’ve wondered whether we should keep doing these events the same way now that Story County Conservation staff and volunteers are testing many of these streams on a regular basis. This is the third map I’ve made from a coordinated snapshot event (see also May 2024 and September 2023) and I’ve noticed some issues with our standard suite of tests that limit our ability to narrow down where pollution is coming from or where conservation practices are making a difference:

Nitrate test strips are not very precise at the high range (color matches at 10, 20, or 50 mg/L). This can be improved with a smartphone app. We also had some big discrepancies that we traced back to a bottle of just-expired strips that I had assumed would still be okay; when in doubt, throw them out!
Dissolved oxygen in streams has a daily cycle (rising in the afternoon when plants and algae are photosynthesizing), so sampling at the same time of day is more important than sampling on the same day.
During scattered showers, water clarity may not tell us where the soil is better protected from erosion, just where the rain was more or less intense.
It’s difficult to match colors to get a phosphate reading when the water is cloudy with sediment. I’ve tried filters but they clog with silt before you can get a 25 mL water sample.

Our next volunteer monitoring event might look a little different. I’d welcome ideas for how we can collect more useful data or get more new people involved!

A smartphone app does color matching to get a more precise nitrate reading

Colors are harder to match when water gets muddy

« Older Entries