2.5 Hydrologic Systems

The Department of Natural Resources? Public Waters Inventory identifies six basins within the Langdon Lake subwatershed as under the jurisdiction of the DNR (see Figure 10).  These include Langdon Lake, Saunders Lake, Black Lake, and three unnamed wetlands. 

Table 2.  Public Waters in the Langdon Lake subwatershed.

DNR ID #

Name

27-182P

Langdon Lake

27-951W

Unnamed

27-952W

Unnamed

27-953W

Unnamed

27-185W

Saunders Lake

27-183W

Black Lake

Source: Minnesota DNR.

The 2003 MCWD Hydrologic, Hydraulic, and Pollutant Loading Study (HHPLS) included detailed modeling of the current and 2020 hydraulic and hydrologic conditions in the subwatershed.  That modeling includes the following results for 10 modeled nodes within the subwatershed:

  • Existing Normal Water Level;
  • Existing High Water Level, peak discharge, and peak velocity for the 1.5 year, 24-hour and 100-year, 24-hour events;
  • 2020 predicted HWL, peak discharge, and peak velocity for the 100-year, 24-hour event; and the
  • Existing High Water Level for the 100-year, 10-day snowmelt event.

Those detailed results are not reproduced here, but are incorporated by reference.  The HHPLS model predicted that future development in the subwatershed would increase local peak flows and volumes, potentially creating higher than desirable velocities in culverts and drainage channels.  Rate and volume controls should be considered for future development. 

Table 3.  Modeled peak discharge from the Langdon Lake subwatershed (cfs).

Event

Existing

2020

Snowmelt

1.5 year, 24 hour

4.9

-

-

100 year, 24 hour

14.0

14.9

-

100-year, 10-day

-

-

16.1

Source:  2003 MCWD Hydrologic, Hydraulic, and Pollutant Loading Study (HHP