Hydrology of Two Interdunal Valleys in the Nebraska Sand Hills

Authors

Steve Drda, University of Nebraska-Lincoln

First Advisor

David Gosselin

Second Advisor

F. Edwin Harvey

Date of this Version

2-1998

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Geosciences

Under the supervision of Professor David Gosselin and F. Edwin Harvey

Lincoln, Nebraska, February 1998

Comments

Copyright 1998, Steve Drda. Used by permission

Abstract

Two neighboring interdunal valleys are compared within a study area of about 15 square miles in the Nebraska Sand Hills. One is a subirrigated wet meadow drained by a manmade ditch. The other is topographically lower, but dry at the surface. The goal of this study is to identify the factors responsible for the hydrologic regime present in each valley, and to discern the reasons for the differences between the two valleys. Water levels in 39 piezometers positioned at different locations across both valleys, and at different depths were monitored for two-and-a-half years to determine groundwater flow paths, gradients, and seasonal variability. Surface waters in and near the site include the South Branch of the Middle Loup River, a drainage ditch, and Phipps lake-all believed to be in hydraulic connection with groundwater. Seasonal variations in surface- and ground-water levels exist, but are of different magnitude in different parts of the system. The region receives about 20 inches of precipitation annually, but recharge to groundwater is significant due to rapid infiltration through the sandy material. Local variations in the configuration of the water table are complex, particularly in the vicinity of the ditch, and appear to be influenced by topography. The drainage ditch affects the shallow flow system in the wet valley. This ditch may be responsible for a reversal in flow direction on one side of the valley as well as a steep upward gradient under the valley floor. Evapotranspiration controls the spatial distribution of groundwater recharge and discharge. Although surface drainage via the ditch has a major influence on the hydrology of the valley, more water is removed by evapotranspiration, if estimates of ET are reasonably accurate.

Advisors: David Gosselin and F. Edwin Harvey