Evapotranspiration and the water budget of prairie potholes in North Dakota

Professional Paper 585-B




The mass-transfer method was used to study the hydrologic behavior of 10 prairie potholes in central North Dakota during the 5-year period 1960-64. Many of the potholes went dry when precipitation was low. The average evapotranspiration during the May to October period each year was 2.11 feet, and the average seepage was 0.60 foot. These averages remained nearly constant for both wet and dry years.

The greatest source of water for the potholes was the direct rainfall on the pond surface; this supplied 1.21 feet per year. Spring snowmelt supplied 0.79 foot of water and runoff from the land surface during the summer supplied 0.53 foot. Even though the water received from snowmelt was only 31 percent of the total, it was probably the most vital part of the annual water supply. This water was available in the spring, when waterfowl were nesting, and generally lasted until about July 1, even with no additional direct rainfall on the pond or runoff from the drainage basin. The average runoff from the land surface into pothole 3 was found to be 1.2 inches per year- 1 inch from snowmelt and 0.2 inch from rainfall.

'The presence of growing aquatic plants, such as bulrushes and cattails, was a complicating factor in making measurements. New computation procedures had to be devised to define the variable mass-transfer coefficient. Rating periods were divided into 6-hour units for the vegetated potholes. The instruments had to be carefully maintained, as water levels had to be recorded with such accuracy that changes of 0.001 foot could be detected. In any research project involving the measurements of physical quantities, the results are dependent upon the accuracy and dependability of the instruments used; this was especially true during this project.

Additional publication details

Publication type:
Publication Subtype:
USGS Numbered Series
Evapotranspiration and the water budget of prairie potholes in North Dakota
Series title:
Professional Paper
Series number:
Year Published:
U.S. Government Printing Office
Publisher location:
Washington, D.C.
Contributing office(s):
North Dakota Water Science Center, Dakota Water Science Center
vi, 49 p.
Larger Work Type:
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
Hydrology of prairie potholes in North Dakota