Middle Fork of the Crow River
Kandiyohi County, Minnesota

2007 Middle Fork of the Crow River Watershed Handbook - A guide to help landowners make their property watershed friendly. (PDF, 18 MB)
 

2004 Update of the Diagnostic Study (2002) 

By  Bruce Wilson  (1), Skip Wright (2), Bruce Gilbertson (2), Maggie Leach (1) with contributions from Tom Bonde 1)Minnesota Pollution Control Agency; (2)Minnesota Department of Natural Resources; (3) Middle Fork of the Crow River, former coordinator

April 14th, 2004

Credits and Appreciation

 This work would not have been possible but for our volunteer monitors:

 Ron Johnson - Lake Calhoun

Dean Lovold - Nest Lake

Corky Beck and Erick Amundson, Lake Monongalia

Val and Jerry Sechler, Crow River

Graden West, Crow River

Jill Nelson, Volunteer Coordinator - Green Lake

Gary Broman, Project Coordinator

Thank You to these sponsors: 

Kandiyohi County Water Plan - Stream and lake sample analyses were funded by a grant from Kandiyohi County and we thank the Kandiyohi Commissioners and Jeff Bredberg for their support and encouragement.

Minnesota Department of Natural Resources for their support of the flow gauging and flow data analyses by the Division of Waters’ Greg Kruse and Skip Wright and Division of Fish and Wildlife’s Bruce Gilbertson.

Minnesota Pollution Control Agency for providing staff support of Maggie Leach, project manager, and Bruce Wilson for data reduction, modeling and report preparation.

Summary

This assessment of the Middle Fork Crow River watershed, Kandiyohi County, Minnesota, was conducted at the request of the Middle Fork Crow River Lakes Partnership.  The purpose of this work was to continue collecting key lake and stream data and to compare to the 2002 Diagnostic Study results for tracking of improvement or degradation patterns.  Stream measurements were conducted by Minnesota Department of Natural Resources – MNDNR- (Greg Kruse, Lisa Berendtson and Carl Rundberg). The data was summarized by  Skip Wright and Bruce Gilbertson - MNDNR and Bruce Wilson and Maggie Leach - Minnesota Pollution Control Agency.

This assessment primarily focuses on the effects of the plant growth nutrient, phosphorus, as it generally controls production of nuisance aquatic plant and algae as well as lake water clarity.  In general, the summer of 2004 was relatively cool until the end of the growing season.  Monitored stream and lake water quality were better in 2004 than observed in 2002.  Average summer lake transparency for Green Lake has rebounded from the low values of the mid-1990’s of 7 to 10 feet to about 14 feet in 2004. There is much less historical Secchi data for Nest Lake to track trends. Volunteer monitoring for Lake Calhoun has shown average summer Secchi transparency values in the 4-5 feet range since the late 1990’s.  Lake Calhoun’s average total phosphorus value of 28 ppb, was slightly better than noted in 2001 (32 ppb), and suggests that some degree of reduction in phosphorus loading, has occurred from watershed sources and internal loading.

One of the primary present day lake management issues - is the internal recycling of historical accumulations of phosphorus from the lakes’ and wetlands’ sediments.  Even with a cooler summer, this phenomenon remains substantial for Nest Lake in 2004.  It is likely that peak internal loading will occur during hot, drier summer conditions in future years for Nest, Green and Calhoun Lakes.  One of the best ways to limit internal sediment recycled phosphorus is to reduce external sources of loading.  It is suggested that a “no net increase in phosphorus loading” be implemented as main lake management policy for these lakes.

Growth in New London, Spicer and along the lakes and streams of the Middle Fork of the Crow River, has caused substantial increases in impervious surfaces over the past 15 years.  Increases in impervious surfaces (roads, roofs, sidewalks, compacted soils and parking lots) can have profound negative impacts to streams, habitat for fisheries and wildlife as well as water quality.  The amounts of impervious surfaces within portions of the watershed have reached levels (e.g. greater than 15%) that have typically been well-linked to degradation of streams.  Water quality modeling indicates that all study lakes will be very sensitive to increased stormwater discharges.  Of particular note, in the first tier (300 foot distance from the shoreline) around Green Lake, there is an estimated 29% imperviousness (due in equal measures to residences and roads).  Continued growth, expected to occur over the next three decades, should be accompanied by carefully designed, operated and maintained stormwater runoff controls. 

A major factor in determining the potency of the stormwater relates to the amount of imperviousness – highways and streets, parking lots, and rooftops within the drainage areas.   Many studies have shown that the amount of impervious surface area in a watershed is related to the alteration of streams and loss of fish habitat as well as degradation of water quality and wetlands (Center for Watershed Protection, 2004).   In the case of stream impacts, 10 percent or less of drainage basin imperviousness can begin altering streambeds, negatively impacting fisheries and critters (macroinvertebrates), and decreasing important infiltration of ground waters.  As the amounts of imperviousness increase, the runoff velocities and volumes increase, ripping away the sides of the streams to carry eroded soils downstream to sensitive lakes and streams.

Until relatively recently, the linkage between impervious surfaces (or mostly car habitat in the words of Tom Schueler of the Center for Watershed Protection) and impacts to receiving waters was not fully realized.  While managing to prevent/avoid/minimize imperviousness is preferable, most communities have had little time to understand and appreciate the ramifications of increases in impervious surfaces to receiving waters.   In Minnesota, about 200 municipalities with populations about 10,000, also called municipal separate storm sewer system cities (or “MS4’s”), are being required to improve stormwater management via stormwater pollution prevention plans (SWPPP).  Each regulated party determines the appropriate pollution prevention practices or "best management practices" to minimize pollution for their specific site. 

Some recommended first steps in stormwater management include:

(1) advanced planning and mapping of impervious areas within drainage basins of sensitive streams and lakes;

(2) locating existing runoff management practices, potential buffer and conservation areas that would limit interconnectedness of impervious surfaces; and

(3) linking of several BMPs to provide sequential treatment of stormwater runoff.   The effectiveness of these efforts is improved by having numerical/narrative resource management goals for the receiving water bodies for typical pollutants.   Advanced simulation models such as P8 (Walker, 1990) can offer considerable assistance in estimating the effectiveness of BMP treatment systems.  

Note: Both New London and Spicer are not classified as MS4 communities and hence, are not presently required to obtain a permit and complete stormwater management planning by the MPCA. 

Recommendations

1. Implement a policy of “no net increase in phosphorus loading to these lakes”.
2. Protect and restore impaired wetlands including the riparian wetlands of the Middle Fork Crow River between New London and Nest Lake (above County Road 40).
3. Implement the watershed projects specified in the 2002 Diagnostic Report, as possible such as:
   1. Continue efforts of the Kandiyohi Soil and Water Conservation District and Natural Resources Conservation Service offices that have been providing technical support and working with landowners to implement Best Management Practices, as has Kandiyohi County. 
   2. Examine failing septic sources to Nest Lake for system and upgrade as possible.
   3. Kandiyohi County should consider reduced impervious limits in tiers 2 through 5 (10 - 15%) and adopt stormwater controls to prevent stormwater flooding and water quality degradation.  New growth areas should have stringent stormwater runoff treatment by placing several Best Management Practices (BMPs) in a series and not rely upon one BMP.  Retrofitting of stormwater BMPs in existing developed areas should be strongly encouraged via landowner education, partnerships and city ordinances.
   4. Protect existing wetlands from stormwater treatment use unless designed and maintained for such purposes.
   5. Continue to identify and correct sources of phosphorus above County Road 40 to the Middle Fork of the Crow River.
4. Operation and maintenance of stormwater systems require dedicated budgets and personnel.
5. Citizen volunteer monitoring of the lakes and streams is needed each year for the next 4-5 years.  Secchi measurements need to be accomplished about 8-10 times per lake per summer.

METHODS

Sampling 

Five stream sampling stations (New London Dam, County Road 40, Old Mill Dam, Alvig Slough and County Road 2) are located throughout the river and tributaries representing discharges along the Middle Fork Crow River system.  Stream flows were gauged by the Minnesota Department of Natural Resources Waters Division staff on multiple occasions and regressed against staff gauge readings.  Developed equations were used to estimate flows.  Streams were sampled approximately 9 to 15 times  over the non-ice time period and data pooled from previous years for FLUX assessments.

Figure 1. Watershed Map

Lake monitoring stations were established for two sites on Green (e.g. north and south), and one station each for Monongalia, Nest and Calhoun Lakes.  Laboratory analyses were performed by the ERA Laboratory of Duluth (Minnesota Department of Health Certified laboratory) using U.S. Environmental Protection Agency (EPA) approved methods.  Lake samples were analyzed for total phosphorus and chlorophyll-a.  Temperature and dissolved oxygen profiles and Secchi transparency readings were also taken.

Modeling

The data reduction techniques include estimates of 1.) subwatershed mass loadings using FLUX software (Walker, 1986); 2.) hydrologic and phosphorus routing through the main stem and tributary sites; 3.) main stem and tributary water and mass balances; and 4.) estimated total phosphorus loadings along the river system.  Lake simulations were accomplished using BATHTUB software (Walker, 1986), employing natural lake phosphorus, chlorophyll-a and Secchi transparency models.

The master files used for FLUX have been labeled mfall_Q.wk1 (flows) and mfall_s.wk1 (sampling data).  The master files used for BATHTUB analyses were labeled Nest04.bin and Green04.bin.  No model calibrations were employed in BATHTUB simulations.

Impervious Surfaces, Growth and Impacts

Figure 2. Estimated population growth.

Continued steady growth in the region (e.g. 10 to 30 percent over the next three decades) means increasing stormwater runoff to area streams and lakes resulting primarily from additional impervious surfaces associated with roofs, roads and parking lots.  These changes have profound negative effects first upon streams, as imperviousness increase to 10 percent of stream watershed areas (and the lakes they supply) and beyond as shown in the below photos (Figure 3) from the Center for Watershed Protection.

Figure 3. Impervious surface impacts & streams

The University of Minnesota’s Remote Sensing and Geospatial Laboratory, under contract with the MPCA, developed impervious surface maps for most of the Crow River cities including Spicer and New London using Landsat satellite remote sensing data (Bauer and Loeffelholz, 2004). The past decade has been one of steady growth across many areas of North America including Minnesota, and particularly in our lake regions and associated communities such as Spicer and New London.    From 1990 to 2000 (US Census time periods), New London’s impervious surfaces have increased to about 29% of the city area and to about 36% of Spicer’s area.  The amounts of these impervious surfaces show a strong potential to cause irreversible degradation of streams, if not aggressively managed to reduce the rates of stormwater runoff.   Complete maps for New London and Spicer are included in the appendix. 

Figure 4. Impervious surface changes in New London & Spicer

Figure 5.  Impervious surface coverage within first tier of development on Green Lake (2003)

Imperviousness

Impervious surface coverage within the first tier of development on Green Lake was determined by digitizing hard surfaces such as structures, parking areas, roads and driveways, using 2003 Farm Service Administration digital orthophotograpy. 

The area of study was limited to the first tier of development located on the inside of the lake road that encircles Green Lake.  On average this represents a 300 - foot zone adjacent to the lakeshore, characterized by high levels of development on substandard lakeshore lots.  In addition redevelopment pressure along the lakeshore is high.  Typically redevelopment involves replacing smaller seasonal dwellings or cabins with larger more permanent homes resulting in increased impervious surfaces.

Based on 2003 aerial photographs, 29% of the 406 acres of land located within the lake road is impervious (including the roadway).  If the roadway is excluded, there is 18% impervious coverage within the first tier of development.  Residential development accounts for 48% of the imperviousness.   Roads are 46%, public nonprofits are 5% and commercial is 1% (see attached graph).

Figure 6.  Green Lake impervious surface by use

Figure 7.  Overview of changes in elevation along the Middle Fork of the Crow River

The elevational changes occurring within the Middle Fork Crow River, as indicated in Figure 7 provided by Tom Bonde, show that the greatest drops occur in the upper reach above Monongalia Lake (River Miles 35 – 45) as well as between New London and Nest Lake (River Miles 22-25).  As such, these areas may exhibit a greater sensitivity to erosional forces and should be managed by urban stormwater treatment measures, buffer strips as much as possible, and other BMPs that slow the rate of runoff. 

Results

Figure 8. 2004 Rainfall, Temperatures

Temperatures were cool over the summer until late August and into the late part of the growing season of September/October.  Rainfall for this area, as usual, has been quite variable with a wet spring/early summer followed by drier conditions leading into a wet late August and September as seen above.  In total, about 34 inches of rainfall occurred over the watershed in 2004.  The long-term average annual rainfall (1971-2000) at New London is 31.7 inches.  Variations of annual precipitation occurring in 2004 across Minnesota may be viewed on the statewide map included in the appendix. 

Stream flow

Annual flows for 2004 were generally average to slightly above average.  However, peak flows occurred in mid-summer and the fall due to unusually dry conditions experienced in the spring and above normal rainfall in the fall of the year.

Figure 9. Stream flow hydrographs.

Water Quality

Figure 10.  Water Quality Summary

Data from 2002 (black numbers) and 2004 data (red numbers) in the Middle Fork system were calculated and plotted for lake total phosphorus concentrations (phosphorus being the key nutrient affecting nuisance conditions) and flow-weighted mean stream concentrations, as seen in figure 10.  Flow-weighed mean values are calculated by computer estimation of total pounds of phosphorus at a specific stream station, divided by the total flow for that stream location.  As may be seen in Figure 10, lower (improved) stream phosphorus concentrations were noted for all monitored sites in 2004 (e.g. New London Dam, Town Hall Road, Old Mill Dam, Alvig Slough, and the Outlet (at Highway 2).  In a similar fashion, all of the lakes also experienced a decrease in total phosphorus concentrations. 

Why Improved Conditions?  The specific causes of the improving conditions are not known but are likely a result of a cooler summer, upgrading of the Green Lake regional wastewater plant (including the elimination of septic system use around Green Lake and elimination of emergency sewer bypassing into Monongalia Lake), feedlot changes within the County Ditch 37 subwatershed, MNDOT erosion and sediment control efforts in the TH23 project, and implementation of best management practices within the watersheds including the agricultural areas north of Lake Calhoun.  These patterns were noted in spite of development growth (homes etc.) that has occurred in the watershed.  Future monitoring of average chloride concentrations may offer further assistance in deciphering the effects of diversion of Green Lake septic tank wastewater to the new regional wastewater system.

Nest Lake Summary

Quantities of water in and out of Nest Lake were estimated to average about 48 cfs translating into a water residence time of about 0.5 years (the amount of time it would take to refill a drained Nest Lake).  The main sources of phosphorus to the lake are from the Middle Fork of the Crow River (49%), and internal sources/lake sediments ( 36%) followed by estimated losses from septic tanks (10%).   The sediment sources of phosphorus (old sediment sources plus septic tank plumes) to Nest Lake were estimated to contribute as much as the Middle Fork of the Crow River.  Meaningful improvement of the lake water quality (and minimizing nuisance conditions) will require reduction of sediment phosphorus losses.  Failing septic systems contribute to the sediment phosphorus recycling burden; therefore, improved septic tank performance by installing new systems or connection to the regional wastewater facility, should be given close scrutiny by township and county decision makers.  It has been the author’s experience that septic tanks typically contribute much less than 5% of the total estimated phosphorus loading.  Reducing upstream phosphorus sources to Nest Lake (e.g. implementation of agricultural Best Management Practices (BMPs) in the watershed of Monongalia Lake, improved stormwater management for the New London and growth zones, improved wetland area management such as reducing the river and wetland P sources above County Road 40), will also be helpful to reduce sediment phosphorus accumulations over time (decades) by flushing them out of the Nest Lake system.

Nest Lake 2004

 GROSS WATER BALANCE:

 GROSS MASS BALANCE BASED UPON OBSERVED CONCENTRATIONS

 COMPONENT: TOTAL P                     

 Nest Lake Model Simulation     

Predicted lake water quality reasonably approximated observed conditions using the US Army Corps of Engineer model, BATHTUB, using the measured flows into and out of Nest Lake along with the monitored water quality.

Figure 12.  Nest Lake water clarity based on satellite imagery.

Figure 12 is a Landsat satellite estimation of the lake water clarity, averaged across the entire lake surface area for Nest Lake and area lakes.  In 2004, the average summer Secchi clarity was about 6.1 feet (1.8 meters shown in the BATHTUB modeling summary.)

Green Lake Summary

Figure 13.  Green Lake historical secchi disk readings

Average summer lake transparency for Green Lake has rebounded from the low values of the mid-1990’s of 7 to 10 feet to about 14 feet in 2004.    The average summer transparency of 14 feet is the best value in the long-term record for Green Lake.

Quantities of water in and out of Green Lake were estimated to average about 78 cfs (during the ice free time) translating into a water residence time of about 4 years (the amount of time it would take to refill a drained Green Lake).  The main sources of phosphorus to the lake are from the Middle Fork of the Crow River (59 %), followed by Spicer stormwater (~11 %), and then the Immediate Lake Watershed + Alvig slough contributing an estimated ~8 %.   Spicer stormwater contributions for 2004 were estimated from data provided by the Minnesota Department of Transportation.  For this data, an average total phosphorus value of 429 ppb was coupled with an estimated flow.  As future monitoring data is obtained, this value can be refined.   

The 2004 Green Lake average total phosphorus concentration of 14 ppb, was lower than it has been seen for several years.  The BATHTUB model predicted in-lake phosphorus of 18 ppb , was slightly greater than the observed but consistent with previous data (e.g. 2001 monitored condition).   It should be noted that total estimated phosphorus to these lakes from developed shoreline of Green Lake along with the municipal areas of New London and Spicer was estimated to be between 220 and 732 kg P/Year with a most likely value in the 440 kg phosphorus per year (970 pounds per year).  Continued reductions in phosphorus levels of stormwater entering the lake from within the City of Spicer, New London and developed shoreland areas is critical to protecting water quality.

Green Lake                                                             

 GROSS WATER BALANCE:                         

 GROSS MASS BALANCE BASED UPON  OBSERVED CONCENTRATIONS

 COMPONENT: TOTAL P         

Green Lake     

Green Lake                                                             

 OBSERVED AND PREDICTED DIAGNOSTIC VARIABLES

 RANKED AGAINST CE MODEL DEVELOPMENT DATA SET

 SEGMENT: 1 Green Lake               

Computer simulations of water quality were greater, but reasonably close to observed values and consistent with improving water clarity patterns for 2004.  Green Lake’s internal recycling of phosphorus appears to be negligible for this year, in contrast to Nest Lake. 

Table 1. Estimated Stormwater Phosphorus to the Middle Fork Lakes (based on methodology of Reckhow and Simpson (1980))

Lake Calhoun Summary

We could not reasonably model Lake Calhoun’s water and phosphorus dynamics due to the lack of resources for sampling and flow gauging of the County Ditch 26 site.   Volunteer lake Secchi transparency monitoring has shown, however, that Lake Calhoun’s average summer transparency has remained relatively stable over the past six years.  A decline of Lake Calhoun’s average total phosphorus to 28 ppb was noted from the 2001 value of 32 ppb.   Maintaining average total phosphorus concentrations below 30 ppb can be expected to result in perceptible reductions in nuisance algal blooms.

Figure 14.  Lake Calhoun historical secchi disk reading

Figure 15.  Lake Calhoun water clarity based on satellite imagery.

                                                                Appendix A

Percent Impervious Cover (IC%) estimated by Landsat satellite for Spicer for 1991 and 2000 by IC % range.  From the University of Minnesota Remote Sensing and Geospatial Laboratory (2005).  Color dots represent about 1/4 acre.

                                                            Appendix B

Percent Impervious Cover (IC%) estimated by Landsat satellite for Spicer for 1991 and 2000 by IC % range.  From the University of Minnesota Remote Sensing and Geospatial Laboratory (2005).  Color dots represent about 1/4 acre.

                                                                 Appendix C                                                

                                               Appendix D

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