High nitrate this spring: where and why

High nitrate this spring: where and why

The Des Moines Waterworks was forced to use their nitrate removal system for the first time in five years. Our spring snapshot found high nitrate concentrations in streams across Story County. On my way to speak at the CCE Environmental Expo in Mitchell County, I dipped a test strip in the Cedar River near Osage and measured 16 mg/L. Looking at the Iowa Water Quality Information System there’s orange (nitrate greater than 10 mg/L) across much of the state and spots of dark red (nitrate greater than 20 mg/L) in Story, Hamilton, and Hardin counties. What’s going on?

 

 

flowing drain tile

Well, differences in land use, soils, topography, and farming practices make for strong regional differences in water quality.  For some streams like the North Raccoon River, this is a return to normal.  For some streams, like the Cedar River, current conditions are unusual. To illustrate this, I’ve invented my own graph, which compares highest nitrate concentrations observed this spring (the blue dot) to the entire 10-20 year record (a black band showing the range, and a black square showing the median). The data comes from Iowa DNR’s Ambient Stream Monitoring Network; I will update these graphs once June data is available. A sampling of sites is shown at right, but the entire graph can be downloaded as a PDF here.

nitrate in selected rivers

Northwest Iowa is still suffering from drought, and that means the Floyd River near Sioux City (which usually has some of the highest nitrate concentrations in the state) is barely flowing and has very low nitrate concentrations. As we saw last year, nutrient concentrations tend to be low during dry conditions except where there is a strong influence from point sources of pollution. Most of the rest of the state is back to normal, and nitrate that accumulated in the soil during two dry years is now getting flushed out. These maps are taken from the National Drought Mitigation Center at the University of Nebraska-Lincoln.  I’ve drawn in the approximate location of the watersheds for the monitoring sites in my example.

map showing drought abating

Weather whiplash in agricultural regions drives deterioration of water quality.”  That’s the title and conclusion of a paper that studied previous episodes when a wet spring followed a dry summer and fall.  The 2012 drought was much more severe than 2021, impacting yields so that less nitrogen was taken up by the crop and removed in the grain, and maybe that’s why nitrate in 2013 and 2014 was so much higher than it is now.  I’ve compared spring highs for several sites and years, normalizing by the long-term average.  It’s not clear to me whether weather whiplash increases the overall mass (load) of nitrogen that gets washed away, or just alters the timing (moving in one year what would have been parceled out over two), but high concentrations are a concern for communities like Des Moines and Cedar Rapids that get their drinking water from a river or river-influenced wells. 

map showing shift out of drought in 2013
map of weather whiplash in 2014
graph showing when nitrate was higher than usual for select sites

I’m procrastinating on the work I’m supposed to be doing because “Hey look!  Data!” and I have to satisfy my curiosity.  If you’d like to see us do more water quality analysis beyond Story County, let us know, and support us with a charitable donation so it can become work I’m supposed to be doing!

The Incredible Diversity of Iowa Bees

The Incredible Diversity of Iowa Bees

June is National Pollinator Month! While many animals can act as pollinators (from bats to butterflies to beetles), this month we are choosing to celebrate the most efficient pollinators of them all: native bees!

Iowa has nearly 400 species of native bees. While the word “bee” brings the honey bee (Apis mellifera) to most people’s minds, this is just one species of bee and it is not native to Iowa; they were brought to the States by early settlers. Unlike honey bees, nearly all of Iowa’s native bees are solitary, meaning one female bee creates and tends her own nests. There are too many bee groups and species to cover in one article, and therefore we are focusing on only eight common groups of bees in Iowa to appreciate this month: bumble bees, cellophane bees, sweat bees, mining bees, mason bees, long-horned bees, leafcutter bees, and carpenter bees.

Bumble Bees
One of the most beloved groups of bees, bumble bees are large bees that look chunky and fluffy (what’s not to love?). They nest above or below ground in abandoned burrows or cavities, and are Iowa’s only truly social native bees! Their colonies can be large but only live for one year. Near the end of the hive’s life, young queens hatch and leave the hive to hibernate alone during winter, then emerge the next year to start their own hives. An easy way to tell bumble bees apart from large carpenter bees is that they have fuzzy abdomens, while carpenter bees have shiny black, nearly hairless abdomens.

Common Eastern Bumble Bee

Cellophane Bees
Also known as plasterer bees or polyester bees, these fuzzy friends are in the bee genus Colletes. They are known by a wide range of plastic-alluding names due to the plastic-like coating they create to line their underground nest cells. The plastic-like substance acts like waterproofing, protecting eggs and developing larvae from moisture, fungus, and other threats. Cellophane bees are active in spring here in Iowa.

Cellophane Bee

Sweat Bees
Bees in the sweat bee group belong to the family Halictidae. They come in a vast array of colors, sizes, and nesting strategies; there are about 500 different species of sweat bees in North America alone! My favorite genus of sweat bee may be Augochloropsis; these bees have green, comma-shaped wing shields (also called tegulae), are a brilliant blue-green color, and there’s even a bee with the species name metallica! Other sweat bee genera range from metallic to dull brown in color, with many nesting in the ground. While not truly social, some sweat bees nest communally by sharing main tunnels underground, similar to how we share hallways in apartment buildings!

Sweat Bee

Mining Bees
This group of bees often includes bees in the Andrenidae family. These bees excavate their nests in the ground and come in a range of sizes. These bees are currently active in Iowa! Look for their nests by finding small piles of dirt around a hole the size of a #2 pencil (though the size of the hole varies between species). You may find more than one nest in an area!

Mining Bee

Mason Bees
Belonging to the genus Osmia, this group of bees is especially important for the pollination of fruit and other crops! They are also in the same family as leafcutter bees (Megachilidae). They are beautiful metallic bees here in Iowa and are active in spring. Some species are cavity nesters, so they may occupy a bee hotel if provided! Alternately, some species make their nests entirely out of mud, a trait that earned them the nickname “mason bee”.

Mason Bee

Long-Horned Bees
Aptly named for their long antennae, most species of long-horned bees nest in the ground. Only males have amazingly-long antennae, sometimes nearly reaching the length of their entire body! Many bee genera belong to the long-horned bee group. Some species are very fluffy and are consequently called “teddy bear” bees, which is probably the cutest nickname in the insect world!

Longed Horned Bee

Leafcutter Bees
Belonging to the genus Megachile (meaning “big-lipped” in Greek), many leafcutter bees have huge jaws that cut pieces of leaves with which to line their nests. These bees mostly nest above-ground and may utilize your bee hotel. While many bees store pollen on their hind legs, leafcutter bees are unique in that they collect and store pollen using the underside of their abdomen! There they have thick, broom-like hairs called scopa that sweep up and trap pollen during flower visits.

Leafcutter Bee

Carpenter Bees
Did you know that there are two main kinds of carpenter bees? There are the large carpenter bees that you are probably familiar with, which can look similar to bumble bees. However, there is a second, lesser-known group of tiny carpenter bees belonging to the genus Ceratina. These tiny carpenters chew down the pithy centers of stems and twigs to form rows of nest cells. These bees are one of the reasons to dead-head your flowers and leave the stems standing at the end of the growing season; you’re providing a nesting site for tiny bees! Also, some species have the coolest cream-colored spot on their nose.

Carpenter Bee

There are countless details in the bee world to learn and appreciate. This is by no means an exhaustive list of all of the bee groups and their quirks occurring in Iowa, much less the rest of the world. For instance, I didn’t even mention parasitic bees, which are bees that don’t make their own nests or collect pollen for their young; instead, they steal it from other bees! Next time you are outside on a sunny day, take a moment to focus your eyes on a smaller scale and look for flower visitors; you may meet someone new!

It’s Rude to Point, but…

It’s Rude to Point, but…

By my calculations, over 65% percent of the nitrogen load in Ioway Creek on May 20 came from less than 1 percent of the land area in the watershed.  We still don’t know why.

Revised May 31

Many people assume that fertilizer applied to turf grass is a major source of nitrogen and phosphorus pollution in Iowa.  At a presentation to the Ames City Council, I was asked if a public awareness campaign aimed at lawn care professionals and homeowners would be an effective way to improve water quality in Ioway Creek.  If we’re talking nitrogen, I don’t think so:

  1. Because turfgrass covers a tiny proportion of the land in most Iowa watersheds, compared to cropland.
  2. Because turfgrass is a perennial. Having something growing and taking up available nutrients year-round is the principle on which cover crops reduce nitrogen loss.
  3. Because there was a study by Dr. Keith Schilling that found very low nutrient levels in shallow groundwater below six Iowa golf courses.
Turf grass in the rain

To that list, I can add local water quality monitoring including lab testing and sensor results from May.  Nitrate in Ioway Creek and the South Skunk River were the highest we’ve seen for a few years, but while rural tributaries ranged from 12-20 mg/L of nitrate, College Creek (an urban watershed with plenty of turf grass) measured only 2.3 mg/L.

But even if turf grass in general isn’t a serious water quality problem, maybe some specific areas of turf grass are a problem.  That’s what I thought after reviewing the data from our spring water quality snapshot on May 17.  Volunteers found a big difference in nitrate levels between South Duff Ave and other sites in Ames.  I wondered if it could be a mistake, so I went back out on May 20 with a bottle of test strips and a smartphone app that enables more precise measurements.  It wasn’t a mistake (nitrate in Ioway Creek increased from 8.6 mg/L to 24 mg/L in two miles), but the results still weren’t making sense, so I kept testing and testing until I assembled the map below.  By my calculations, 65% of the nitrate load in Ioway Creek that day was coming from just 1,500 acres!

map showing nitrate results on May 20

The 1,500 acres includes Coldwater Golf Links, and the pattern looks like what I’d expect to see if the golf course was overapplying fertilizer.  However, the golf course superintendent has informed me that fertilizer has not been applied since fall, and then only at a low rate.  A volunteer tested two ponds on the course and found low levels of nitrate (1-2 mg/L).

The 1,500 acres include some developed areas north of creek drained by storm sewers, but I tested water trickling from two outfalls on May 20 and found very low nitrate levels: 0.5 mg/L and 3.1 mg/L.

Worrell Creek at golf course

The 1,500 acres acres also includes two construction sites: a flood mitigation project near South Duff Ave and an ISU recreation complex east of Jack Trice Stadium.  The photo shows severe bank erosion where drainage from the ISU construction site enters the creek.  An inspector with the Iowa DNR noted problems with erosion control earlier this spring on the South Duff project.  However, if the nitrate spike were linked to erosion, I’d expect to see high phosphorus and low transparency.

Honestly, I’m not sure what’s going on here.  It’s not a pattern we’ve seen in previous years.

erosion on Ioway Creek between Grand and Duff avenues

When interpreting this kind of data, there is a risk of jumping to conclusions and unfairly pointing fingers.  In my first draft of this article, I suggested that Coldwater Golf Course was the source of the nitrate and the bank erosion.  That was premature.

However, there is also a risk that we will waste time and money on the wrong solutions or the wrong areas if we don’t test water or don’t follow where the data is pointing.  It’s clear from this month’s data and many other rounds of testing that water quality impacts are not uniformly distributed across the landscape.

Volunteers in the Creek All Week

Volunteers in the Creek All Week

Trash Cleanup

Ioway Creek recently got some love from the community.  On Saturday, May 21, a group of seventeen volunteers (plus another four helping on land) loaded nine canoes with trash as we floated from Brookside Park down to S. 16th Street in Ames.  We hauled out 14 tires and 1,560 pounds of other trash including 3 shopping carts, a tent, and two bicycles.  Assembling the tools, canoes, food, and people was a collaborative effort involving Prairie Rivers of Iowa, the City of Ames, Story County Conservation, the Skunk River Paddlers, and the Outdoor Alliance of Story County.  A few people got wet, everyone got dirty, my muscles are still sore, but we all had a good time on the river!

volunteers testing water quality

Citizen Science

On Tuesday May 17, fourteen volunteers tested water quality in Ioway Creek and its tributaries. This is the fifteenth Spring Watershed Snapshot, and the fourth that Prairie Rivers organized. Thanks to the Outdoor Alliance of Story County for help with supplies.  This year, some volunteers were already doing regular monitoring of a site for Story County Conservation and adjusted this month’s schedule to coordinate, or picked up a few extra sites. If we include other watersheds and other days tested during the same week, the count is 22 volunteers (and also some Story County Conservation staff) and 47 sites in Story, Boone, and Hamilton counties.

We scheduled the event for a weekday this year to coincide with Polk County’s snapshot, so while the event was less social than it sometimes is (volunteers could pick up a kit any time on Tuesday and test their assigned sites alone or with a friend), they were monitoring as part of a big coordinated effort of the kind that we haven’t seen since before the IOWATER program was cancelled!  In Polk County, 75 people covered 115 sites!

A table with our findings are shown below, and a map of the sites can be found here.  On Tuesday, the water was clear and phosphorus was low at all our sites.   Chloride was highest and nitrate lowest in creeks with more urban watersheds.  Dissolved oxygen fell into the “fair” range at several sites in Hamilton County, as well as the south fork of Worrell Creek in Ames.  Nitrate was 10 mg/L or higher at most sites, but reached 20 mg/L in the middle sections of Ioway Creek and several rural tributaries.  I did some followup testing to make sense of the high nitrate levels at Duff Ave, more on that later.

Thanks to all the volunteers who spent some time in a creek last week!

5-2022 Water Quality Snapshot Results

Take it Easy for Pollinators This Spring!

Take it Easy for Pollinators This Spring!

Signs of spring and warmer weather can be energizing, motivating us to start spring-cleaning our homes inside and out. However, some pollinators are still resting in their winter homes, and cleaning up your lawn too soon can be detrimental to the new generation. For some spring lawn care tips that support pollinators continue reading below!

Pollinators either migrate to warmer climates or go through a phase called “diapause” to survive the harsh winters of Iowa.

Diapause is similar to hibernation in which an insect pauses any development and stays in a kind of suspended animation until conditions are more favorable. There may be many insects in your yard that are still hibernating under leaves or inside flower stems waiting for warmer weather in order to emerge. Rushing to clean up all your leaves and brush now can disturb and damage these pollinators so it is best to leave some “messy” areas in your yard as long as possible. Waiting until the end of May, a time of year when day temperatures consistently reach 50 F (usually), is best. Taking it easy and waiting until later in the spring to tidy up is the easiest way to support pollinators at home!

One specific way to protect pollinators until they emerge is to leave the leaves that have accumulated in your yard. Bumble bee queens especially love to overwinter under layers of leaves as it provides them an insulating layer that protects them from the wind and cold. While you may not want leaves covering your entire yard this spring, leaving the leaves in your garden beds, in particular, can not only protect the pollinators resting there but may also provide you with some composting and weed-suppressing services. Additionally, leaving last year’s flower stems in the garden and not cutting them back until late May will give most stem-nesting bees a chance to emerge as well.

An additional option to support pollinators is to participate in No Mow May, a campaign started by Plantlife in the UK and spearheaded here in the US by Bee City USA, run by the Xerces Society. The goal of No Mow May is to keep your mower in the garage until June and allow floral resources such as dandelions and clover to spring up in your yard providing early pollinators with food resources. Waiting to mow also means the longer grass is able to provide more cover for other insects needing shelter.

While we all want to support pollinators and enjoy them in our yards this year, it can be difficult to allow your lawn to look a bit wilder and to your neighbors, it may look a bit messy. They may not understand that your yard isn’t a mess – it’s a habitat for pollinators! There is much pressure to maintain the traditional, yet outdated, yard of green turf grass containing little to no diversity. To address these concerns we provide the following solutions:

  • Start taking it easy on your backyard
    If your front lawn simply must remain manicured, set aside your back yard to leave the leaves and flower stems and not mow until May. This will still help pollinators and make the pollinator habitat less visible from the street.
  • Create a “Cozy Corner”
    If you can’t put aside your entire back yard, try leaving an unused area in the yard undisturbed. You can create a “cozy corner” for pollinators throughout the coming growing season by leaving the leaf litter there undisturbed and by adding twigs, branches, and other brush to the area as you clean up. This cozy corner can provide shelter for not only insect pollinators, but birds as well! Adding layers of brush to your cozy corner will ensure it serves as an excellent shelter for birds and a fantastic nesting site for pollinators, especially for overwintering. It is also a fun family activity that can be built upon throughout the year!
  • Educate your neighbors
    Let your neighbors know that your yard is providing a specific and important purpose and that it may mean they will be able to enjoy more butterflies and bees in their garden this summer. Here’s a link to free signs created by the Xerces Society you can print out and place in your yard. Spread the word about how you are helping pollinators. Ask others to join you!

There are many ways to support pollinators at home. Many people are starting the fun process of gardening for the foraging needs of pollinators by growing native flowers. However, few people think about the nesting resources that pollinators require. Be mindful with yard clean-up by taking it easy this spring and finding an area to leave undisturbed throughout the year. It will aid in pollinator emergence and provide them with nesting sites. Have a happy and relaxing spring!

Rivers Routinely Ruin Riprap Revetments

Rivers Routinely Ruin Riprap Revetments

This island in the middle of the South Skunk River used to be riprap armoring the outside bend.  (I turned my kayak upstream to take this photo).  Rick Dietz pointed this out to me during the Skunk River Paddlers’ annual “Pancake Paddle” on April 2.  Five of us bundled up and enjoyed canoeing and kayaking from South 16th St in Ames to Askew Access near Cambridge.  Back at the office, I looked at some aerial photos.  The riprap near Ken Merrill Road must have been installed some time in the ’90s, but by 2009, the concrete had slumped to the bottom of the channel and the river had started carving away the bank behind it.

aerial photos showing stream movement

The Skunk River south of Ames reflects an old attitude toward rivers.  We straightened the bends in the river, which made the water go faster.  The faster current caused banks to cave in, so we dumped concrete (and sometimes old cars) on the banks to armor it.  This didn’t always work.  Hopefully we’ve learned something from these failures and are exploring how to manage rivers by working with nature:  this can include setting aside floodplain areas to allow rivers to meander, using stumps and rock structures to redirect the current away from unstable banks, reshaping the channel so that the river can overtop its banks and dissipate its energy without causing property damage, and protecting the banks with a mix of rocks and native vegetation.  Riprap and levees should be used sparingly.

As for the paddling, the water was cold, so water proof gear and dry bags are a must, but early spring on the Skunk is a great time to see birds.  We saw several flocks of mergansers, wood ducks, a yellowlegs, bald eagles, and herons.  We’ve got some nice water trails in Iowa, so take advantage!