Chemistry and Flow Monitoring Results – Washtenaw County

Data are collected from stream and river locations that facilitate the establishment of relationships between land cover and ecological stream health. The locations are selected based on their use by the Michigan Department of Environmental Quality, the HRWC Adopt-A-Stream volunteer stream monitoring program, likelihood of significant sub-watershed phosphorus loading based on modeling, and capturing the range of sub-watershed and upstream conditions.

The program monitors annually during the growing season at eleven long-term sites throughout the Middle Huron. Long-term sites help HRWC to determine changing conditions over time. Since 2010, HRWC also monitors at investigative sites located upstream of selected long-term sites.  Investigative sites provide useful data to gain a better understanding of upstream conditions regarding pollutant sources and are usually only sampled for one monitoring season.

Chemistry and Flow Monitoring was conducted in 2019 at two Huron River sites and fourteen tributary or direct drainage sites, which represent a mix of land uses and communities. During the 2019 monitoring season, five of the sixteen monitoring sites were investigative sites. For more information about the sites, please see the map below. Orange and purple sites indicate investigative sites, with green markers reflecting long-term sites.

Middle Huron Chemistry and Flow Monitoring Sites

Total Phosphorus (TP)

Phosphorus is an essential nutrient for all aquatic plants.  It is needed for plant growth and many metabolic reactions in plants and animals. In southern Michigan, phosphorus is typically the growth-limiting factor in fresh water systems.  That is, if all the phosphorus present is used, then plant growth will cease no matter how much nitrogen is available.  Total Phosphorus (TP) is a measure of all forms of phosphorus present in a water sample, and is the primary indicator of overnutrification in the middle Huron River watershed.  The typical background level of TP for a Michigan river is 0.03 mg/L or ppm.  The TMDL established for Ford and Belleville Lakes sets goals of 0.03 mg/L.

Further, phosphorus is the main parameter of concern in eutrophic lake and stream systems for its role in producing blue-green algae.  Phosphorus enters surface waters from point sources of pollution, such as wastewater treatment plants, and nonpoint sources of pollution, including natural, animal and human sources.  Excessive concentrations of this element can quickly lead to extensive growth of aquatic plants and algae.  Abundant algae and plant growth can lead to depletion of dissolved oxygen in the water, and, in turn, adversely affect aquatic animal populations and cause fish kills.  This nuisance algal and plant growth interferes with recreation and aesthetic enjoyment by reducing water clarity, tangling boat motors, and creating unpleasant swimming conditions, foul odors, and blooms of toxic and nontoxic organisms.

Total Suspended Solids (TSS)

Total suspended solids include all particles suspended in water which will not pass through a filter. As levels of TSS increase in water, water temperature increases while levels of dissolved oxygen decrease. Fish and aquatic insect species are very sensitive to these changes which can lead to a loss of diversity of aquatic life. While Michigan’s Water Quality Standards do not contain numerical limits for TSS, a narrative standard requires that waters not have any of these physical properties: turbidity; unnatural color; oil films; floating solids; foam; settleable solids; suspended solids; and deposits. Water with a TSS concentration <20 mg/L (ppm) is considered clear. Water with levels between 40 and 80 mg/L tends to appear cloudy, and water with concentrations over 150 mg/L usually appears muddy. In streams that have shown impairments to aquatic life due to sedimentation, TSS is used as a surrogate measure for Total Maximum Daily Load (TMDL) regulation, since large amounts of sediment can bury potential habitat for aquatic macroinvertebrates.  This is the case for Malletts Creek and Swift Run TMDLs. Those evaluations set the following targets for TSS:

• Optimum = < 25 mg/l
• Good to Moderate = >25 to 80 mg/l
• Less than moderate = >80 to 400 mg/l
• Poor = >400 mg/l

Suspended solids may originate from point sources such as sanitary wastewater and industrial wastewater, but most tends to originate from nonpoint sources such as soil erosion from construction sites, urban/suburban sites, agriculture and exposed stream or river banks.

Sediment-phosphorus relationship

Since phosphorus binds to soil particles, it is important to try and understand whether the phosphorus in the streams is coming along with sediment, through erosive processes or not.  To do this, one can examine each TP concentration with its corresponding TSS concentration. If they are well correlated, then there is some evidence that the phosphorus in the stream originated via erosion. If not, the phosphorus may be moving through the system in dissolved form, unbound to sediment particles.

Bacteria (E. coli)

Escherichia coli (E. coli) counts are measured from water samples as a broad indicator of the presence of pathogens found in the digestive tracts of warm-blooded animals. Their presence may indicate the presence of sewage or wastewater, but high counts can also result from other animal sources. These generalized bacterial counts are not specific enough to be directly indicative of health risks.  However, consistently high levels serve as a warning of potential health risks and warrant further investigation to determine the source of bacterial outbreaks.  The State of Michigan water quality standard for  partial body contact is a monthly average of 130 counts per 100ml of water, while a single sampling event for waters protected for full body contact is <300 E. coli counts per 100 ml of water.  Several reaches in the middle Huron are on the state’s list of impaired waters due to bacterial contamination, including Honey Creek, and drainages to and including the Huron River between Argo and Geddes Dams.

Dissolved Oxygen (DO)

Most aquatic plants and animals require a certain level of oxygen dissolved in the water for survival. Dissolved oxygen (DO) is a measure of the amount of gaseous oxygen (O2) in the water, which enters water from the atmosphere via aeration or as a waste product of plant photosynthesis. DO levels drop to very low levels in warm, stagnant water, whereas fast-flowing, cooler water generally has high concentrations of DO. Some forms of pollution can also provide conditions that impact DO levels.  For example, excess nutrients such as phosphorus and nitrogen can result in reductions in DO levels, which can be detrimental to certain species of aquatic insects. Normal DO values in Michigan waters ranges between 5 to 15 mg/L.  The statewide minimum water quality standard is 5 mg/L.  However, concentrations change throughout the day and night due to air and water temperature changes, photosynthesis, respiration and decomposition.

pH

pH provides information about the hydrogen ion (H+) concentration in the water.  pH is measured on a logarithmic scale that ranges from 0-14, with 7 being a neutral value. Solutions with a pH less than 7 are considered acidic and solutions above 7 are considered basic.  Organisms that live in rivers and streams can survive only in a limited range of pH values. Michigan Water Quality Standards require pH values to be within the range of 6.5 to 9 for all waters of the state. In Michigan surface waters, most pH values range between 7.6 and 8.0.  The pH of rivers and streams may fluctuate due to natural events, but inputs due to human activities can also cause ‘unnatural’ fluctuations in pH.

Temperature

Water temperature dictates what aquatic life will inhabit waterways and controls the dissolved oxygen content of water (as the temperature of water increases, the concentration of dissolved oxygen content decreases). It also influences the rate of both chemical and biological reactions.

Conductivity 

Conductivity is a measure of the ability of water to pass an electrical current, and is a general measure of water quality. It indicates the presence of inorganic dissolved solids, such as sulfates, nitrates, phosphates, and salts. Conductivity is affected by temperature: the warmer the water, the higher the conductivity. Conductivity in surface waters is affected primarily by the geology of the area through which the water flows. In Michigan, values for a healthy river or stream habitat range between 100 and 800 µS/cm.  Low values are characteristic of oligotrophic (low nutrient) lake waters, while values above 800 µS/cm are characteristic of eutrophic (high nutrient) lake waters where plants are in abundance. There are a number of potential sources of minerals and some natural variation, but consistent results above 800 µS would be unexpected from natural sources.  Anthropogenic sources can include winter road salts, fertilizers, and drinking water softeners.

Nitrogen (Nitrate and Nitrite) 

Measurements of Total Nitrogen (TN) yield information comparable to concentrations of Total Phosphorus. However, the laboratory used for the program does not measure TN, so nitrate and nitrite were measured in lieu of TN.

Nitrate (NO₃) occurs naturally in both ground and surface waters, and is the most common form of dissolved nitrogen. Natural levels of nitrate in surface water can come from precipitation and runoff, and is not considered a problem at low levels. Streams and lakes in southeastern Michigan are typically limited by phosphorus levels rather than nitrogen, though the overall productivity of a waterbody (i.e. the amount of plant life at any given time) is controlled by the balance of these nutrients. At high concentrations (at or above 1-2 mg/L), nitrate can contribute to eutrophication that decreases dissolved oxygen levels and threatens aquatic plant and animal organisms. High levels of nitrate in surface waters often are related to human activities. Overfertilization of lawns and crops, failing septic and sewage systems, and animal waste inputs contribute to elevated levels of nitrate. A typical value of nitrate for Michigan rivers is 0.5 mg/L, although lower nutrient water has nitrate concentrations ranging from 0.01 to 0.1 mg/L.

Nitrite (NO₂) is the form of nitrogen that sometimes occurs as a transition compound in the conversion of ammonia (NH₄) to nitrate.  Unlike nitrate (NO₃), nitrites are short lived in aqueous systems, so they are often found at very low levels, if at all.  However, prolonged exposure to high levels of nitrite can produce a serious condition in fish called “brown blood disease”, as it blocks the blood’s ability to carry oxygen resulting in fish kills.

Water Velocity/Flow

Measuring water velocity at the long-term monitoring sites, along with collecting water samples that are analyzed for nutrient concentration, allows for calculating the “load” of a particular nutrient for a specific moment in time. A “load” is a measure of the amount of a substance entering a water body, usually expressed as pounds per year. Concentration, when coupled with stream discharge, can be used to estimate the export rates of phosphorus (or other nutrients) for the sub-watershed, and to estimate the loading rates of phosphorus in receiving waters.

The procedures used in this monitoring program have been reviewed and approved by the Michigan Department of Environment, Great Lakes, and Energy (EGLE). Complete procedures are documented thoroughly in the program’s Quality Assurance Project Plan (QAPP). The QAPP was originally developed at the beginning of the program in 2003, and revised and approved by EGLE in 2008 and again revised and approved in 2010. The following is a summary of those methods and procedures.

Stream monitoring was conducted twice monthly from April through September at the designated monitoring sites described above. The volunteer monitoring teams travel to sites and first complete a field datasheet that documents the location, date, time, team members and weather conditions for the current and previous days. The field datasheet also is used to record information about the water samples and the water quality measurement results. If stream flow was also measured during a field outing, a separate stream flow datasheet was filled out to record that activity and velocity measurements. Upon completion of the fieldwork, the monitoring team delivered water samples to the Ann Arbor Water Treatment Plant Laboratory.

Sample Collection Methodology

Collection of water samples was completed first at each site to minimize the disturbance of the stream substrate, which could artificially raise the amount of suspended matter in the water column. For all samples, the team member followed the same “grab” sampling protocol in accordance with the method prescribed in the 1994 EGLE field procedures manual for wadeable streams.

In-stream samples were collected upstream and at arm’s length from where the team member was standing. Where stream depth permitted, water was taken from the middle of the water column and in the middle of the stream cross-section. Exceptions to this method occurred at the Hudson Mills Huron River site where samples were collected fifteen feet from water’s edge. The bottles were rinsed three times with stream water prior to taking the baseline sample. Samples were labeled and placed in a cooler with ice packs until they were delivered to the laboratory for analysis.

Baseline samples were collected to measure Total Phosphorus (TP), Total Suspended Solids (TSS), Nitrites (NO₂), Nitrates (NO₃) and E. coli. HDPE plastic bottles were used for TP, TSS and NO₂+NO₃ samples. If TP samples could not be analyzed within the method-specified holding period after delivery to the lab, they were treated with preservative.

In-Stream Chemistry Monitoring Methodology

Six water quality chemistry parameters were routinely measured at all sites. Water quality measurements for water temperature, dissolved oxygen, conductivity, total dissolved solids, pH, and chloride were made using a YSI Professional Plus (Pro Plus) multi-meter.  For all measurements, the multi-probe instrument was placed in the water at the appropriate submerged level at arm’s length distance and upstream from the team member. The results were read from the digital displays and recorded on the field data sheet.

Flow Monitoring Methodology

Water velocity was measured directly in the stream after water samples were collected and water quality testing was completed. Flow was measured at each long-term site by team members across a range of measured water levels. Where stream discharge instrumentation or a water level gage was in place, discharge measurements can be charted against water level to establish a “rating curve.”  Once established, the rating curves were used to estimate discharge from water level observations. USGS water-level sensors are located at the Malletts Creek and Mill Creek sites, and a similar sensor maintained by the City of Ann Arbor was placed at Allens Creek in 2007.

Total Phosphorus (TP)

A broad examination of total phosphorus concentrations across all long-term sites in the Middle Huron shows that . This chart shows that, each season, the bulk of the concentrations range between 0.03 mg/l and 0.1 mg/l, with a few samples exceeding this range by a considerable margin (concentrations highlighted as red stars). These few high concentrations tend to drive the mean concentration of the season to be higher than the median. Over the years, the median concentration declined until reaching a low point in 2009 when it was below the TMDL target at 0.043 mg/l (mean TP=0.052 mg/l). TP concentrations then returned to higher levels through 2014 (median=0.070 mg/l, mean=0.085 mg/l). Median seasonal TP concentrations then decreased again through the current year’s median of 0.040 mg/l (mean=0.047 mg/l), once again below the target to achieve the TMDL for Ford Lake. In 2019, in fact, the mean concentration was below this 0.050 mg/l target for the first time ever. Therefore, on average 2019 presented the lowest TP concentrations on record.

There is no discernable trend in either the mean or median TP concentrations. Trends are more appropriately examined at the site or creekshed level. However, the median for the last three years was below the stream target. The few extreme concentrations each season clearly push up the annual mean values. Typically, these high concentrations are measured during or following rain storms. As such, stormwater runoff is still a major pathway of overall phosphorus loading to the middle Huron system.

TSS

As shown in this chart, the vast majority of samples from long-term sites in the middle Huron River watershed had TSS concentrations below the target threshold. The mean TSS concentration across all sites for 2019 was 9.8 mg/l with a median of 7 mg/l, so most samples are quite clear of sediments throughout the watershed. The 2019 figures are also consistent with past years. There were fewer high concentration spikes (> 80 mg/l) in 2019, with only one occurrence. With such low levels of TSS, trends are not important, however, it appears that TSS concentrations are decreasing even further at a few sites, including both river sites, Mill Creek and Allens Creek.

Sediment-phosphorus relationship

The tributaries in the middle Huron watershed have a wide range of sediment-phosphorus relationships. At the high end, Malletts Creek (R²=0.72) and Swift Run (R²=0.48) both have strong TSS-TP relationships. These neighboring streams are both impaired for sedimentation and both appear to transport phosphorus from streambank or channel erosion. Most other streams have TSS-TP correlations that are in the 0.20-0.40 range. In these creeks, high TSS values are consistent with high TP concentrations, but at the low TSS end, the TP concentrations are more variable. A few other tributaries (i.e. Traver and Millers) and the river sites show very little relationship between TSS and TP. In these watersheds, the phosphorus is likely entering the surface water in dissolved form through surface runoff or groundwater.

Bacteria

E. coli bacteria levels have improved over time at Middle Huron watershed sites (see figure). In previous years, the majority of the measures significantly exceeded the water quality standards for both partial- and full-body contact, and in some cases by multiple orders of magnitude (see figure). However, in 2019, most measures at most sites were below the full-body contact threshold of 300 counts per 100 ml. In 2019, the median values were below the full body contact standard at six of eleven sites. However, bacteria counts in the middle Huron continue to be an impairment of concern overall.

Nitrogen

Nitrate

An examination of nitrate levels  show that median concentrations for monitoring sites measured from 2003-2019 ranged from 0.20 mg/L at the upstream Huron River stie to 1.10 mg/L at the downstream Huron River site. Superior Drain was not monitored after 2013. Mean concentrations range from 0.26 mg/L at the Superior Drain site to 1.18 mg/L at the downstream Huron River site. Most sites were well below 1 mg/L for all samples, and all sites except Mill, Allens and Boyden Creeks, and the downstream Huron River site averaged below 0.5 mg/L. Nitrate levels at the downstream Huron River site are a concern and HRWC has discussed possible sources with the Michigan Department of Environment, Great Lakes and Energy and the City of Ypsilanti. At this point, no sources have been identified.

Nitrite

Levels of nitrite that are below laboratory detection are considered low. Normal levels of nitrite concentration range from 0.01 to 0.03 mg/L, while levels higher than 0.03 mg/L should be fairly uncommon since this level is at the threshold for chemical transition from ammonia to nitrate.  All monitoring sites in the Middle Huron averaged in this range for nitrite. The vast majority of all samples (>75%) at all sites were below 0.03 mg/L.  While each site has recorded occasional values above 0.03 mg/L, it is not common (only one measure in 2019). There is no discernable trend in nitrite values at any of the monitoring sites.

Conductivity

The median values for conductivity for all 12 long-term monitoring sites over the 2002-2019 monitoring period exceeded the upper limit for healthy waters (800 µS) for 6 of the 12 monitoring sites. The other six sites have been consistently below that ecological impact threshold, such that 75% or more of conductivity measures at those sites were below 900 µS. The sites with the highest mean values are all in urbanized landscapes. These urban sites also have the greatest range of conductivity measurements of all streams studied.  It cannot be determined from these results which ions are driving the elevated conductivity values in these streams, so further investigation is warranted to determine the nature and potential sources of dissolved ions.

Dissolved Oxygen

Over the periods when the DO sensor was functional (2002-19), the vast majority of DO measurements at all 12 long-term sites were above the state water quality standard threshold of 5 mg/L. This indicates that there is consistently oxygen to support life in all Middle Huron streams. However, there have been occasions where DO levels were measured below the 5 mg/L bio-threshold. Eight out of 11 sites were below the threshold in early July of 2015, a particularly dry period. Only Allens, Fleming and Millers Creek sites had sufficient oxygen during that week of sampling. Outside of that dry period, only Mill, Malletts, Swift Run, Boyden and the lower Huron River sites have experiences instances below the life threshold. Of those, only Swift Run has had multiple observations of low oxygen readings. No cause  of those low DO levels was discovered, though they have been concurrent with low flow levels. Median values for all sites ranged between 7.45 mg/L (for Swift Run) and 9.40 mg/L (Millers Creek).

Interestingly, Swift Run also had the highest DO measurement at 19.8 mg/L in April of 2015. DO measurements have typically been highest in April of each year, coinciding with the start of the growing season, colder water temperatures and the increased incidence of storm events and higher water velocities, which may serve to mix greater amounts of oxygen into the water.

pH

Measuring pH helps HRWC to detect spills or discharges of acidic or basic substances. Median values between 2002-2019 for the 12 long-term sites ranged between 7.7 and 8.22, with little variability in individual samples.  All but six sample results were within the acceptable range to meet state water quality standards, with the exceptions of one sample in Honey Creek in 2005 at 6.2, two samples (6.0 and 6.1) at the upstream Huron River site in 2013, two in Traver Creek (6.0 and 6.45) in 2012, and one basic result (9.05) in Swift Run in 2017.  These were all short-lived events and no specific source was ever identified.

Temperature

Water temperature is a controlling variable for the functions of many organisms. Many freshwater species cannot tolerate water that reaches temperatures that are too cold or too warm. Tropical species cannot tolerate the temperatures that approach freezing during Michigan winters. Similarly, many native fish species seek cooler water or die off when temperatures exceed 29°C (85°F). During the entire period of record (2002-2019), only two sites exceeded the 29°C threshold: the upstream Huron River site (five times) and Malletts Creek (once). The Huron River site is wide and shallow at the monitoring location, providing the water with lots of sun exposure. Further downstream, the river likely cools significantly.

Flow data to come!

Visit HRWC’s interactive data viewing feature, Infostream, for more information!

Total Phosphorus (TP)

HRWC assesses TP concentrations in Middle Huron tributaries against a standard of 0.038 mg/l, which is the long-term 75th percentile concentration at the river site MH01, which is defined as the “reference site” for this part of the watershed. That standard is also consistent with regional analysis conducted by the U.S. EPA in 2001. Tributaries are assessed on the most recent five years sampling data and graded on how many samples are below the target threshold according to the following scale:

• A = 80-100%
• B = 60-80%
• C = 40-60%
• D = 20-40%
• F = 0-20%

The table below lists current grades for each tributary stream through data collected through 2020.

Total Phosphorus Charts by Long-Term Site

Looking at individual river and tributary sites can give one an idea of the potential sources of phosphorus. It is more instructive to examine the results by individual tributary site, since sample results are more representative of tributary watersheds than the Middle Huron watershed as a whole. This graph shows TP concentrations for each long-term middle Huron site over the entire range of sampling (2003-19). At the top and bottom of the system, the two river sites show that phosphorus levels increase from well below the TMDL target to slightly above it. In fact, concentrations at the N. Territorial Rd. site have decreased significantly. Phosphorus concentrations at the Michigan Avenue site have also decreased on average, though not as strongly.

In the upper part of the watershed, monitoring stations in Mill, Boyden and Honey Creeks all tell different stories. Mill Creek is the largest tributary in the middle Huron, and has the greatest amount of agricultural land use. Concentrations within its watershed have varied considerably, and have decreased over the last four years. Concentrations in Boyden and Honey Creeks have steadily decreased since 2014. TP concentrations in the urban tributaries are generally higher. TP concentrations in Allens Creek and Traver Creek were high and relatively stable year to year until 2014, when they seemed to decrease somewhat dramatically. This was not the case for the other creeks (Millers, Malletts, Swift Run, and Fleming). However, when concentrations taken during or following storms are removed, the same decrease from 2014 levels is observed. Again, it appears that in urban streams, baseflow concentrations may have decreased through the current year, but concentrations during runoff events are still high, which, in turn, may drive overall loading (see section on phosphorus loads).

Total Phosphorus Charts by Long-Term Site

TSS

HRWC assesses TSS concentrations in Middle Huron tributaries against a stormwater standard of 80 mg/l. With this standard, the stream should not exceed the threshold during storms (or ever). Since storm samples are rare, grade ranges are narrow. Tributaries are assessed on the most recent five years sampling data and graded on how many samples are below the target threshold according to the following scale:

• A = 99-100%
• B = 96-99%
• C = 92-96%
• D = 85-92%
• F = 0-85%

The table below lists current grades for each tributary stream through data collected through 2020.

Total Suspended Sediment Grades by Long-Term Site

Storms do tend to generate turbid runoff at some locations, evidenced by the number of samples over the 80 mg/l threshold. 2019 was a good year in terms of storm erosion, though. In 2019, only one sample exceeded the 80 mg/l threshold at Allens Creek. In the previous year (2018) Honey, Traver, Millers, Malletts and Swift Run Creeks all had high TSS spikes. All except Honey Creek are urbanized tributaries. Swift Run and Malletts Creek are both are listed as impaired for altered hydrology/sedimentation and they exhibited erosion issues during or following storms in past years, but not 2019. 2019 could be an anomalous year, or it could suggest that hydrology and stream bank erosion is stabilizing. More years of data are needed to determine conclusions.

Total Suspended Solids Charts by Long-Term Site

Bacteria

HRWC assesses bacteria concentrations in Middle Huron tributaries against the state’s single sample standard of 300 E. coli units for full contact waters. With this standard, the stream should not exceed the threshold for a single sample out of 5 sample dates. Over the entire period of record, the region’s reference site (Huron River at N. Territorial) met the standard 98% of the time, so grade ranges are based on that target. Tributaries are assessed on the most recent five years sampling data and graded on how many samples are below the target threshold according to the following scale:

• A = 97-100%
• B = 90-97%
• C = 75-90%
• D = 50-75%
• F = 0-50%

The table below lists current grades for each tributary stream through data collected through 2020.

Bacteria Grades by Long-Term Site

Trends in E. coli bacteria levels are generally going in a positive direction. Bacteria levels are decreasing at statistically significant rates at Honey, Allens, Traver, Malletts, and Millers Creeks, as well as the upstream Huron River site. No sites appear to be getting worse. Most sites except the river sites, however, continue to regularly exceed the standards for full-body contact, so there is still work to be done to reduce the sources of bacterial contamination. The highest bacteria counts regularly come from urban sites in Allens, Traver, Malletts and Swift Run Creeks.

E. coli Charts by Long-Term Site

Nitrogen

Nitrate and nitrite levels are generally at low enough levels to not be a concern at all sites, with the exception of the downstream Huron River site. This site requires further investigation to determine source identification. Nitrate levels appear to have decreased over time at some sites, but increased at others, notably Fleming and Mill Creeks, and Swift Run. The cause for the trends is uncertain, and may simply be natural variation.

Conductivity

Conductivity levels at most sites in the Middle Huron are elevated above the target threshold of 800 µS periodically during the sampling season. The urban sites in the system generally have the highest readings. Allens, Traver, Malletts and Swift Run Creek sites all have particularly high levels, but so does Honey Creek, even though it is a mixed land use creekshed. Worst of all is Millers Creek, with a mean conductivity over the years of 1,645 µS (1,875 µS in 2019) and has been measured above 2,000 µS multiple times. Previously, HRWC staff and volunteers traced the source of the highest conductivity (upstream of Plymouth Road), but found no obviously active culprit. The high conductivity levels were coincident with high chloride levels, so the best conclusion is that the source was previous road salt storage. Both river sites, along with Fleming and Boyden Creek sites have consistently low conductivity levels. There do not appear to be any annual trends at any sites.

Dissolved Oxygen

As indicated in the subwatershed summary, most sites monitored in the Middle Huron consistently have DO levels that support life (< 5 mg/l). However, there have been occasions where DO levels were measured below the 5 mg/L bio-threshold. Eight out of 11 sites were below the threshold in early July of 2015, a particularly dry period. Only Allens, Fleming and Millers Creek sites had sufficient oxygen during that week of sampling. Outside of that dry period, only Mill, Malletts, Swift Run, Boyden and the lower Huron River sites have experienced instances below the life threshold. Of those, only Swift Run has had multiple observations of low oxygen readings. No cause of those low DO levels was discovered, though they have been concurrent with low flow levels. Median values for all sites ranged between 7.45 mg/L (for Swift Run) and 9.40 mg/L (Millers Creek). Interestingly, Swift Run also had the highest DO measurement at 19.8 mg/L in April of 2015. There were no low DO events in any creek or river site in 2019. Trend data is not relevant for dissolved oxygen, as it fluctuates over small time frames even in natural conditions.

pH

No sites in the Middle Huron River watershed experienced significant issues with high acidity or basicity. Over the entire period of record, all but six sample results were within the acceptable range to meet state water quality standards. Those six included one sample in Honey Creek in 2005 at 6.2, two samples (6.0 and 6.1) at the upstream Huron River site in 2013, two in Traver Creek (6.0 and 6.45) in 2012, and one basic result (9.05) in Swift Run in 2017.  These were all short-lived events and no specific source was ever identified. There were no pH issues identified in 2019. Trends at most sites have generally shown fluctuation over the years, with pH values a bit higher now than in the 2008-12 period. See Huron (MH01), Traver and Swift Run sites for examples.

Temperature

Water temperatures fluctuate throughout the growing season, much like air temperatures, though not as much. Cooler temperatures in April give rise to warming temperatures through August, and then generally drop a bit in September. During the entire period of record (2002-2019), only two sites exceeded the 29°C threshold: the upstream Huron River site (five times) and Malletts Creek (once). It appears that overall the trend over the last six years appears to show a slight warming trend, but the full period of record shows no significant trend in temperatures. The Huron River site is wide and shallow at the monitoring location, providing the water with lots of sun exposure. Further downstream, the river likely cools significantly. Also, it is important to keep in mind that these temperature measures are taken at the time of sampling, which could span a wide range of day times from 10 am to 6 pm. Daily peak temperature would be a better measure for tracking trends at sites.

Flow data to come!

Visit HRWC’s interactive data viewing feature, Infostream, for more information!

Funding Partners & Governments

The Middle Huron Chemistry and Flow Monitoring Program is a project of the Middle Huron Partners. The Partnership is a voluntary watershed-based group of businesses, academic institutions, and local, county and state governments working since 1996 to prevent pollution in the middle Huron River Watershed and meet federal water quality standards for Ford and Belleville lakes. Member governments and agencies include:

Ann Arbor Charter Township
Ann Arbor Public Schools
Barton Hills Village
City of Ann Arbor
City of Belleville
City of Chelsea
City of Dexter
City of Ypsilanti
Northfield Township
Pittsfield Charter Township
Scio Township
Superior Charter Township
University of Michigan – Environment, Health & Safety
Washtenaw County Road Commission
Washtenaw County Water Resources Commissioner
Ypsilanti Charter Township
VA Ann Arbor Healthcare System

Partners and Volunteers

The strength and breadth of the Middle Huron Chemistry and Flow Monitoring Program is made possible by the generous time and effort provided by the over 60 annual volunteers. The Middle Huron Partners and the Huron River Watershed Council would like to sincerely thank the volunteers and leaders for their dedication to the program.

The Middle Huron Partners would also like to thank the City of Ann Arbor Water Treatment Plant Laboratory for providing water sample processing and analysis.

For additional information on the Chemistry and Flow Monitoring Program and results, please contact Ric Lawson at [email protected].

To become a volunteer in the program, please visit hrwc.org/chemflow.