Hydrogeological assessment of the Little River drainage basin:
comparison of river stage, groundwater flow, and precipitation
Abstract
This study expands on previous hydrogeological work on the Kip Tract piezometers transect located on the field at the Pike Street and Route 68 intersection, and the Little River. Head and stage are related to precipitation data downloaded from the weather station located in the field behind the St. Lawrence University physical plant. Data loggers were placed at strategic locations in the Little River and piezometer transect. Data was organized and examined to investigate choice hydrological and hydrogeological properties of the area: baseflow drainage of the Little River after a rain event; lag time comparison of the transect and Little River; and to quantify the specific discharge to the Little River of a 4x1m cross section of the sandy aquifer of the transect. Following significant precipitation events, river stage responds with rapid rises in level followed by a slower decline to baseflow levels. In contrast, groundwater has a slightly longer lag-time and water levels remain high for longer duration.  After a precipitation event of 45.77mm over 22hrs, head exhibits a lag-time almost double that of stage, and rises 8.67x10-3m/hr faster than head. Both reach maximum levels after approximately 60hrs after initial water level rise, and stage declines 4.34x10-3m/hr faster than head. Preliminary hydraulic conductivity studies suggest the majority of the groundwater is flowing through an extremely porous sand layer, which is sandwiched between less conducive clayey-silt on top, and an underlying till. Average hydraulic conductivity of the sand layer, based on slug tests and the Hvorslev method is 3.9x10-4cm/s-1. Darcy’s Law was used to quantify specific discharge of the transect in response to a storm event, which shows an average discharge of 0.1896cm3s-1.
Introduction
The Little River and Kip Tract region is a great place to examine hydrogeological properties typical of all drainage basins. In order to do this, data loggers were placed at three locations on the Little River: at the Pike Street bridge, Park Street bridge, and Little River- Grasse River confluence. A transect of piezometers was measured, located on the greatest topographic gradient feeding into the Little River, at the intersection of Route 68 and Pike Street (Fig. 1). Data was collected, and analyzed in conjunction with precipitation data obtained from the field station behind SLU physical plant in order to quantify basic hydrogeological parameters for the Little River and Kip Tract in specific. Concepts discussed in the this poster include stage and head response to a precipitation event, specific discharge of the transect to the Little River, and general trend analysis.
Lag-time and return to baseflow comparison of stage and head after precipitation event,
After a precipitation event of 45.47mm over 22hrs, river flow exhibits a lag-time of ~26hrs at which time there is a rise of 0.83m over 58hrs for a rate of 0.014m/hr. At this time, the stage declines at a rate of 7.67x10-3 m/hr until interrupted by another event.
In contrast, after the same rain event, groundflow has a lag-time of 40hrs from the start of the event, and rises 0.32m over the next 60hrs, for a rate of 5.33x10-3m/hr. At this time it declines at a rate of 3.33x10-3m/hr before being interrupted by another event.
Head at MW 3-1, and precipitation event comparison
Stage at Park Street bridge and precipitation event comparison
Figure 1: Aerial photo of Canton, NY, with location of data loggers and piezometer transect
Discussion
Head exhibits a lag-time almost double that of stage, and rises 2.6x faster than head. Both reach maximum levels after approximately 60hrs after initial water level rise, and stage declines 2.3x faster than head.
Using Darcy’s Law to predict piezometer transect discharge to Little River
The discharge of the transect during each stage of the precipitation event described at right, pre-event head, maximum head, and post-event head, is quantified. The transect consists of a sand aquifer between overlying clay, and underlying till aquitards. Groundflow is almost exclusively restricted to this highly conducive sand layer. In order to quantify the amount of water flowing into the Little River from this 4x1m sand layer, Darcy’s Law was employed. Piezometers terminating in the sand layer from MW1 and MW3 were utilized.
Darcy’s Law: q=-K*∆h/∆l, with  q=Q/A
Q= Discharge
A= Cross-sectional area, 4m high, 1m wide
K= Hydraulic conductivity of sand layer, = 3.9x10-4cm s-1
∆l= Length of transect, 14480cm
∆h= Change in hydraulic head, function of elevation head + pressure head
Based on the above calculations, the average discharge of the 4x1m sand layer into the Little River is 0.1896 cm3s-1. It is interesting to note the increased discharge preceding the precipitation. At this time, the hydraulic gradient is higher, due to drainage of the aquifer. Also note that this analysis does not take into account the complex horizontal thinning nature of the sand aquifer, as this is only a preliminary basic analysis.
0.1884 cm3 s-1
0.1788 cm3 s-1
0.2016 cm3 s-1
Q
4.471x10-6cm s-1
4.47x10-6cm s-1
5.04x10-6cm s-1
q
1.75m
1.66m
1.87m
∆h
113.56m
113.73m
113.2m
h, MW1
115.31m
115.39m
115.07m
h, MW3
10/19/03 post-event
10/18/03, max response
10/15/03, pre-event
 
Acknowledgments
I would like to thank Bill Olsen for his assistance with weather data and Bill Casey for his assistance with river data. Thanks to Aileen O’Donoghue, without whom I would still be wading throw excel data, and Diana Odorczuk, for access to her previous work in the area. Last, but not least, I would like to thank my thesis advisor, Stephen Robinson, for his guidance and patience.
Figure 2: Aerial photo with contours superimposed showing the line of transect and the four piezometer nests
Contour interval: 5 feet, Transect length: 214.2m     (Odorczuk, D. ’03)
Brendan Lennon,
Dr. Stephen Robinson (advisor)
St. Lawrence University, Department of Geology
To the left is a display of river and precipitation data from the end of June to the beginning of December. In general, many basic hydrological parameters are apparent in this graph.
Stage decline from spring rain and snowmelt
Low-flow, river responds to the minimal precipitation and high evapotranspiration
River level rises due to increase of fall storm events, lack of evapotranspiration
Despite the fact that all the loggers are relatively close, there are apparent differences between hydrographs
Pike street exhibits a drastic increase I response to a major rain event
However, in response to a small event it is comparatively attenuated
This is probably a response to channel morphology
Response to minimal rain during summer, and high evapotranspiration
Shutdown of evapotranspiration and increased rain, but due to the gradient at MW3, baseflow increase is not as drastic
MW1 is located at the “bottom” of the transect (Fig. 2), receiving the groundwater from higher elevations, and has a longer storage duration due to minimal gradient
Comparison of stage response at different locations
Pressure head comparison of sandy aquifer, MW1, MW3
Long-Term Stage and Precipitation Data
Confluence
Park Street Bridge
Pike Street Bridge
Transect
Cross-sectional view of transect
Odorczuk, 2003
Conclusion
This study is an attempt to create, and expand on a database for the Little River catchment. Instrumentation for long-term data collection has been installed for future collection in order to come to a better understanding, and to quantify characteristics of a river basin near  SLU in specific. This poster only scratches the surface of the possibilities inherent to what the data sets can tell us about hydrologic parameters of the region. It investigates and analyzes a comparison between stage and head response to a storm event, specific discharge to the Little River of a 4x1m cross-section of the sand aquifer in the transect, and general comments on relatively long-term trends and characteristics of hydrographs and groundflow. This is an ongoing process, building on information from piezometers installed in 2003, in collaboration with data loggers  placed in the Little River and climate data from SLU field stations. There are also plans to measure infiltration rates in the future.
Sandy aquifer