Counting critters and what they reveal about Watkins Creek

On March 20, we sampled the macroinvertebrate population at our site off Coal Bank Road, near the downstream end of Watkins Creek. We enjoyed another very warm and pleasant day, the latest in a string of days that have come close to, met, or exceeded record high temperatures that has lasted for more than a week. Already the redbuds in our backyard a couple of miles away are in bloom.

We've been doing these macroinvertebrate samplings - the informal name for them is critter counts, because we collect the macroinvertebrates in a kick net, then pull them off the net to identify them to order and count them - for the past three years at this site. I've also taken part in sampling a tributary of the River des Peres in University City as a member of Stream Team 1437 from 2001 through 2010.

The most interesting thing about the March 20 critter count was the high (for an urban stream) diversity of critters. The usual pattern for the River des Peres has been a low diversity in the spring sampling and a somewhat higher, though still low, diversity in the fall sampling. Our suspicion is that winter road salting adversely affects the macroinvertebrate population, as the conductivity and chloride levels go much higher once road salting begins. We've measured chloride levels well over chronic toxicity during winter chemical monitoring events on the River des Peres sites. During the spring and summer, rain flushes the salt out of the soil and stream, perhaps allowing for a repopulation of some of the macroinvertebrates from nearby locations that are less affected by runoff from salted roads. If this is what's happening, it would explain why we observe a higher diversity during fall samplings compared to spring samplings.

For the Coal Bank site of Watkins Creek, we recorded a higher diversity of critters in fall 2009 compared to spring 2009, but lower diversity of critters in fall 2010 compared to spring 2010. Critter diversity in both spring and fall 2011 continued at about the same low level as noted in fall 2010. This spring, the critter diversity took a marked jump up from fall 2011, returning to about the same level as noted in fall 2009. What might be going on here?

In addition to road salting, the Coal Bank site is also affected by occasional flooding when the nearby Mississippi River floods up into the creek. While the winter of 2009-2010 did not bring excessive snowfall and therefore not much road salting was required, the Mississippi River experienced several weeks of flooding during late spring and summer, flooding that backed up into the Coal Bank site. Some critters cannot survive in the slack water caused by flooding. It may be that any repopulation of some kinds of critters that would normally occur during spring and summer was set back by flood-related habitat destruction, leading to the lower diversity of critters we noted in fall 2010 compared to fall 2009.

Not only did we experience excessive snowfall during the winter of 2010-2011 (we measured a chloride level about 3 times higher than the acute toxicity level on January 28, 2011, during the worst of the snowy pattern), but the Mississippi River flooded for weeks again during late spring and summer of 2011. If salt toxicity and flooding do indeed lead to a lowered diversity of macroinvertebrates as I suggested above, we would expect to see that reflected in our critter counts for spring and fall of 2011, as indeed they are. Compared to the water quality rating of 21 (good according to Missouri Stream Team criteria) we obtained in fall 2009, the water quality rating in spring 2011 was 12, and in fall 2011 it was 13 (fair in both cases).

So why might we have seen a rebound in diversity this spring, to a water quality rating of 22? First, the Mississippi has stayed below flood levels during the past fall and winter, perhaps allowing some critters to repopulate into the creek from less-affected waters nearby. In addition, we had very little snow this past winter, so very little salt was applied to area roads. Our one winter measurement of chloride was just under the chronic toxicity level. Perhaps the low level of added salt allowed for better critter survival over the winter. If the Mississippi River stays out of flood this year, we might see at least as high a diversity of critters this fall, if not higher than what we measured on March 20. Call this a hypothesis; we'll see what next fall brings. It would be good news for Watkins Creek.

Rain barrels and rain gardens do Watkins Creek good

We all know that when rain falls on our yards, parks, and gardens, it soaks into the ground (at least, we hope it does). But what happens to the rain that lands on roofs, driveways, parking lots, and roadways?

When rain falls on hard surfaces like these, it runs downhill along the surface. Rain falling on a roof eventually enters a gutter and then a downspout. After leaving the downspout, if the water hits another hard surface like a driveway or parking lot, it runs downhill along that. Unless these hard surfaces drain onto a planted surface, eventually that water drains into a storm sewer. From there, the water drains into a stream - into Watkins Creek if it falls in Watkins Creek’s watershed.

Allowing rainwater to drain into storm sewers and then into Watkins Creek helps keep streets and parking lots from flooding. But it isn’t so good for the creek. All that water entering the creek in a short period of time causes the creek to rise too much and too fast. The too-fast flow erodes the sides of the creek, eating into your backyard if you live along the creek. Your backyard soil may clog the bottom of the streambed when the flow slows down and the soil settles out. The soil might smother small insects, which would otherwise serve as food for fish. The creek loses quality and causes losses to property owners.

You can help reduce the amount of stormwater that enters Watkins Creek and obtain free water to use on your yard or in your garden by putting a rain barrel under one or more of your downspouts or by creating a rain garden on your property. A rain barrel is a large container that sits under a downspout to collect rain that flows off a roof. The container has a hose bib (water faucet) attached near the bottom so you can drain water out when you want to use it. Most people put the container on cement blocks so the hose bib can be placed as near the bottom as possible. You can build your own rain barrel or buy a rain barrel from the River des Peres Watershed Coalition or from various companies. Search “rain barrel” to find directions and suppliers. You’ll want to use the water before the next rain so the barrel will fill again and keep that water from running off into the storm sewer system. You can drain it into a watering can and water plants with it, or attach a hose and let the water drain onto your lawn or into your garden if these are downhill from your barrel. Special soaker hoses that work on low-pressure water from rain barrels are becoming available; check with hardware or garden suppliers.

You can also create a special garden, called a rain garden, to capture all of your roof’s runoff and use it to grow attractive plants that like extra moisture. To make a rain garden, you dig a shallow basin downhill from one of your downspouts and far enough away from your house so the water doesn’t damage your foundation. After you’ve dug the basin, you plant it and mulch it, then attach an extender to your downspout to direct the water into your rain garden. 

Here’s a photo of my rain garden, taken soon after planting it in April 2009. You can see a rain barrel behind the rain garden; the barrel overflows into the garden.

To learn more, request Native Plant Rain Gardens from the Missouri Department of Conservation. Rain Gardening and Storm-Water Management, available from Missouri Botanical Garden, is a more in-depth guide to creating and managing a rain garden. Search “rain garden manual” on the website to find it. You can install a rain barrel under your downspout to collect water for your container plants, then direct overflow water to a rain garden, as I did. Homeowners, apartment complexes, schools, churches, and businesses can install rain barrels or rain gardens. Check out Hazelwood Southeast Middle School’s rain garden sometime!

Coal Bank Road site: Watkins Creek at its best

One of the first sites our Stream Team began monitoring is about where Coal Bank Road crosses over Watkins Creek. This is near where the creek empties into the Mississippi River. We chose this site to monitor for two reasons. The first is to learn about the state of the creek near its end, to get an overall picture of the levels of any contaminants. As I mentioned in the previous post, we are particularly interested in the levels of E. coli and chloride (salt), two pollutants found in Watkins Creek at levels exceeding Missouri state standards. By monitoring near the mouth of the creek, we can see the cumulative effect of these pollutants.

The second reason we monitor at Watkins Creek is because this is one of the easiest sites to walk to along the main stem of the creek (the longest path the creek takes from source to mouth). The photo below shows the west bank at this site, where we walk to the creek.

Notice the gentle slope (for Watkins Creek, at least) from the stream bank up into the riparian corridor. Creeks in watersheds with only small amounts of impervious (hard) surfaces like roads, rooftops, parking lots, and the like exhibit this sort of gentle slope up from the stream bank into the riparian corridor (the area just above the first rise from the stream bank). In such a watershed, rain falls onto absorbent soil and percolates through the soil down to the water table. The water table keeps the stream flowing during dry periods. The soil holds a lot of water during wet periods and what water it can’t hold flows slowly over the ground and eventually enters the creek. When it rains, the water level in the creek rises slowly and goes back down even more slowly. This keeps the velocity of the water rather low and the water level doesn’t vary greatly, thus the stream tends to not erode the surrounding land to a large extent. As long as the impervious surface in the watershed is less than about 10%, the stream will have this sort of gentle slope up from the bank and it will be easy to walk right up to the stream.

Watkins Creek has a much higher level of impervious surface in its watershed than the ideal of 10% or less. Overall the impervious surface is probably closer to 25% (I cannot find the exact number as I am writing but this is about right). Looking at a map of the watershed, the impervious surface is unequally distributed; a higher proportion of the hard surfaces are upstream of Lilac Road than downstream. Once the stream crosses Lilac Road, it can spread out a bit and the water velocity slow down somewhat. By no means does it do this enough to be called unimpaired by the time the creek crosses under Coal Bank, but it does slow down enough above Coal Bank that we can access it without using a rope.

Next time I’ll discuss some of the biological and chemical testing that we’ve done at this site and the results that we’ve obtained.