Lake Water Level Management Tool

Recently Brookfield Renewable Energy gave a presentation to the stakeholders that included a very informative sharing of the difficulties involved in managing the water levels in Deep Creek Lake.

The Deep Creek Watershed Foundation has been working since its creation to create a management tool to equitably allocate the use of the water in Deep Creek Lake to generate power. Brookfield’s success in managing the resource affects all stakeholders. The management must be carried out within the framework of the Water Appropriation Permit administered by the Maryland Department of the Environment.

The company is required to submit an annual report. For those with time on their hands, you can find the reports at: https://mde.maryland.gov/programs/water/water_supply/pages/deepcreeklakeperiodicreports.aspx. The reports are complete and afford a wealth of data about the power generation operation.

Century Engineering from Baltimore completed the first Water Budget Model for the foundation in June of 2018. Because there was no record of watershed rainfall, no record of water levels, and no record of discharge until two months after the end of the calendar year, a traditional water budget model could not be constructed. They produced a bookkeeping scheme that used the water remaining above the Lower Rule Band on a particular day and subtracted the daily required releases going forward until that water was consumed. When a rainfall event occurs, the lake level goes up and the end of the water day moves forward in time. The foundation distributed that model to the power company.

Starting in 2018, the foundation set to work to provide the necessary data to complete a traditional water budget model. We worked with the United States Geologic Survey to augment the gauges in the watershed area that were in place.

The first one was a recording water level gauge for the lake. Lake management is predicated on the water level relative to the overflow weir at the power company dam, which is assumed to be at elevation 2462. The national level grid is about 1.8 feet different, so we asked USGS to record both datums in the data set. The significant advantage of using them is that the record is kept on the Internet and available to everyone. Given the difference between the elevation measured by survey methods and the staff gauge at the dam, the staff gauge is a single point of failure for managing lake levels according to the permit. The USGS gauge has records back to August 2020.

The foundation sponsored two additional rain measurements to augment the USGS rainfall records at North Glade Run, one at Cherry Creek and the other at Hoyes Run.

The USGS flow gauge on the Youghiogheny River immediately downriver from the power plant discharge has been operating since July 2011. The flow data shows the base flow of the river and the discharges from the power plant. A second USGS gauge was installed upstream at Swallow Falls to evaluate the base flow.

In May 2022, the foundation contacted CEC, a civil and environmental engineer from Pittsburgh, Pennsylvania, to complete the traditional water budget model. The fundamental idea of the water budget model is Water In – Water Out = Change in lake level. With the additional rainfall measurements, the record of water levels, and the record of discharge from the plant for the water year from 1 October 2023 to 30 September 2024, CEC can ascertain the dynamics of the fundamental idea. The goal is to create a model that considers past rainfall, current lake level, and future discharge to produce power per the permit.

Consider an old, clawfoot bathtub full of sand and gravel. Below the drain, attach a recording flow gauge. Water poured into the tub will flow out at a rate and duration based on the amount of water. A record of flow vs. time for one five-gallon bucket dose, a ten-gallon dose, and enough water added to reach the top of the tub plotted on a discharge vs. time graph would calibrate the tub and its contents to predict the rate water will come out of the drain.

The Deep Creek drainage area is like the bathtub. Water runs off, evaporates, and soaks into the ground when it rains. Twelve hours after a rain, all precipitation has run off into the lake or streams. The water that soaks into the ground flows by gravity. Consider the water level in a water supply well. That level is where the groundwater surface is. Most of the water supply wells around the lake have a level higher than the lake, and groundwater flows into the lake. All the lake’s water comes from direct rain, stream flow, or groundwater recharge. An analysis of precipitation records, lake levels, and lake discharges could model the recharge of the lake based on past rainfall.

To be useful to the power plant operator, CEC is creating an Operator User Interface (OUI). The OUI will consist of a computer program that operates behind the scenes to query the USGS websites to retrieve inputs on past rainfall, current water levels, and permitted requirements for discharge. The primary challenge is to model the recharge into the lake from groundwater. The engineer will use the USGS rainfall, flow and water level data collected from October 2023-September 2024 to create the water budget model recharge component.

The OUI works using the same bookkeeping technique as the original limited model. On a given day, the operator enters the date. The program returns the remaining days before the water level goes below the lower rule band. Given the advance notice of the limited water supply, The Maryland Department of the Environment and the plant operator could devise a plan to distribute the remaining available water among the stakeholders equitably.

The plan to deal with the water shortage will make it less of a problem for the various interests in the water in Deep Creek Lake if MDE and the power company put it in place before the need for it!

CEC has a year record and is preparing the OUI now.