Introduction

The U.S. Army Corps of Engineers Norfolk District contacted the U.S. Geological Survey (USGS) in April 2010 regarding the determination of flow from a midchannel spring located in Jackson River below Gathright Dam near Hot Springs, Virginia. The spring is located midchannel approximately 250 feet downstream from the dam’s discharge race channel. The spring can be located by means of a pipe that has been placed near the center of the spring; water can be observed discharging directly to the Jackson River around the pipe (fig. 1). As part of this effort, the USGS compared measured streamflows at the existing streamgage, 02011800 Jackson River below Gathright Dam near Hot Springs, Va., to measured streamflows for the newly established streamgage, 02011799 Jackson River above spring near Hot Springs, Va. (figs. 2 and 3) to compute the springflow. During the period from April 24, 2010, to May 7, 2019, the USGS made 30 concurrent site inspections with streamflow measurements at each streamgage location for comparison and calculation of springflows. The calculated springflows were compared with the daily elevation of Lake Moomaw at 08:00 a.m. (U.S. Army Corps of Engineers Norfolk District Water Management, 2020) and local precipitation totals from the National Oceanic and Atmospheric Administration (NOAA) weather station in Hot Springs, Va., USC 0444128 (National Oceanic and Atmospheric Administration, 2020).

Data Collection and Springflow Determination

Site inspections of the USGS streamgages in Jackson River at 02011800 Jackson River below Gathright Dam near Hot Springs, Va., and 02011799 Jackson River above spring near Hot Springs, Va., below Gathright Dam, were made between April 27, 2010, and May 7, 2019, to determine the springflow. The site inspections included concurrent streamflow measurements above and below the spring to determine its flow (fig. 4). The mean streamflow was determined prior to computing the springflow for inspections that included more than one measurement.

Springflow Determination

Springflow was computed by determining the gain in flow of the reach between the upstream (02011799) and downstream (02011800) streamflow measurements. For inspections that included more than one streamflow measurement at a site, the average streamflow at that site was determined prior to computing the springflow. A plot showing the average measured streamflow at each inspection upstream and downstream of the spring is shown in figure 5. The gain in flow was calculated by determining the difference in measured streamflow between sites 02011800 and 02011799. Table 3 lists the summary of the average measured streamflow, calculated springflow, the water-surface elevation of Lake Moomaw at 08:00 a.m.Eastern Local Time , in feet above the National Geodetic Vertical Datum of 1929 (NGVD 29), and a 30-day precipitation total prior to the inspection for NOAA weather station USC 00444128 in Hot Springs, Va., on the day of the inspection. Springflow calculated from the 30 inspections made during the study period ranged from −7.00 to 43.0 cubic feet per second. The negative springflows are considered zero flow, as the differences are within the acceptable uncertainty of the streamflow measurements, the percent uncertainty of each measurement can be found in tables 1 and 2. Streamflow measurement uncertainties include uncertainties in the cross-section, the water-velocity profile, computational assumptions, and other systematic errors (Turnipseed and Sauer, 2010). While each year of the study contained limited springflow data points due to a small number of site inspection, the average annual springflow observed was calculated and entered in table 4. The average annual springflow is used to review how the flow of the spring varied over time.

Table 3.    

Summary of the average measured streamflow data for U.S. Geological Survey streamgages 02011799 and 02011800, calculated springflow, the water-surface elevation of Lake Moomaw at 08:00 a.m. Eastern Local Time (U.S. Army Corps of Engineers, 2020) and a 30-day precipitation total for the National Oceanic and Atmospheric Administration weather station USC 00444128 in Hot Springs, Virginia (National Oceanic and Atmospheric Administration, 2020).

[Dates shown as month, day, year. ft³/s, cubic foot per second; NGVD 29, National Geodetic Vertical Datum of 1929; in., inch]

Table 3.    Summary of the average measured streamflow data for U.S. Geological Survey streamgages 02011799 and 02011800, calculated springflow, the water-surface elevation of Lake Moomaw at 08:00 a.m. Eastern Local Time (U.S. Army Corps of Engineers, 2020) and a 30-day precipitation total for the National Oceanic and Atmospheric Administration weather station USC 00444128 in Hot Springs, Virginia (National Oceanic and Atmospheric Administration, 2020).

Date of inspection	Observed streamflow at 02011799 (ft3/s)	Observed streamflow at 02011899 (ft3/s)	Calculated springflow (ft3/s)	Elevation of Lake Moomaw at 8:00 a.m. (ft above NGVD 29)	30-day total precipitation preceding the site inspection in Hot Springs, Virginia (in.)
4/27/2010	4.19	19.5	15.3	1,582.2	3.14
8/13/2010	89.2	109	19.8	1,572.2	0.84
3/8/2011	81.1	101	19.9	1,578.3	3.51
6/28/2011	93.0	101	8.00	1,580.4	3.35
6/29/2011	257	272	15.0	1,580.3	3.42
8/17/2011	258	268	10.0	1,572.3	2.15
2/2/2012	75.1	90.2	15.1	1,581.9	3.49
4/4/2012	99.6	107	7.40	1,582.0	2.21
4/19/2012	82.0	103	21.0	1,582.0	2.24
5/17/2012	79.9	99.7	19.8	1,582.8	4.96
8/8/2013	215	244	29.0	1,580.9	3.87
1/31/2014	90.4	113	22.6	1,582.0	1.89
3/26/2014	88.7	107	18.3	1,582.0	2.56
5/28/2014	92.5	105	12.5	1,582.0	4.49
6/18/2014	92.6	103	10.4	1,581.2	3.77
12/11/2014	168	161	0.00* (−7.00)	1,562.2	3.49
1/7/2015	162	161	0.00* (−1.00)	1,567.2	2.19
3/3/2015	140	159	19.0	1,574.8	3.78
11/18/2015	149	169	20.0	1,572.9	3.75
1/7/2016	275	284	9.00	1,582.0	3.20
2/24/2016	2.19	20.2	18.0	1,584.0	4.67
12/14/2016	140	152	12.0	1,582.1	3.76
2/8/2017	191	210	19.0	1,582.1	3.03
4/13/2017	305	313	8.00	1,582.2	4.23
10/4/2017	201	215	14.0	1,568.4	0.66
11/29/2017	165	171	6.00	1,568.1	3.05
12/20/2017	152	157	5.00	1,567.0	0.44
1/25/2018	150	163	13.0	1,568.4	2.47
2/7/2019	182	225	43.0	1,582.0	2.73
5/7/2019	270	286	16.0	1,582.4	8.19

^*

Negative springflows are considered to be zero flow as they are within the associated error of the observed streamflow measurements.

Table 4.    

Average annual springflow observed and annual precipitation totals from National Oceanic and Atmospheric Administration weather station USC 00444128 in Hot Springs, Virginia (National Oceanic and Atmospheric Administration, 2020).

[NOAA, National Oceanic and Atmospheric Administration; ft³/s, cubic foot per second; in., inch]

Table 4.    Average annual springflow observed and annual precipitation totals from National Oceanic and Atmospheric Administration weather station USC 00444128 in Hot Springs, Virginia (National Oceanic and Atmospheric Administration, 2020).

Year	Average annual springflow observed (ft3/s)	Annual precipitation totals from NOAA weather station USC 00444128 (in.)
2010	17.6	35.91
2011	13.2	51.98
2012	15.8	38.5
2013	29.0	46.11
2014	12.8	38.18
2015	13.0	49.23
2016	13.0	47.62
2017	10.4	43.44
2018	13.0	69.22
2019	29.5	46.57

Results and Findings

To determine if the elevation of Lake Moomaw and the springflow show a direct relationship a statistical analysis of the springflow was examined using a linear regression model (fig. 6) between the calculated springflow and the elevation of the Lake Moomaw on the day of the site inspections. The linear regression analysis shows significant scatter or variability in the data points and a coefficient of determination (R²) value of 0.2186. Analysis of the sample data indicated the lake elevation and springflow do not have a significant correlation.

Daily precipitation data from the NOAA weather station USC 00444128 was used to determine the total precipitation for the 30 days preceding the site inspections (table 3). The total does not include the day of the inspection, because the NOAA datasets are reported as daily totals and the precipitation may have occurred after the inspections. A linear regression analysis was also used on the 30-day precipitation total and the calculated springflows to determine if a relationship between recent precipitation and the springflow exists (fig. 7). The linear regression analysis results show significant scatter or variability in the data points and an R² value of 0.0076. The results of the analysis indicate that the precipitation prior to the measurement inspections does not affect calculated springflow.

A review of springflow and an analysis of how it relates to the elevation of Lake Moomaw and recent precipitation totals determined that neither variable displays a significant correlation with springflow. The average annual springflow observed (table 4) was reviewed to examine how the springflow varied over time. The annual springflow shows little variation of over time, with 8 of the 10 years falling within one standard deviation of the mean and the remaining 2 years within two standard deviations. Table 4 also includes total annual precipitation data from NOAA weather station USC 00444128 in Hot Springs, Va. A linear regression model (fig. 8) was used to compare the annual precipitation data with the annual mean springflow to determine if there are any correlations between the two datasets. The results of this analysis are similar to results from the analysis of springflow and 30-day precipitation totals, with the linear regression analysis indicating a significant scatter or variability in the data points and an R² value of 0.0015. Based on this analysis, annual climatological changes did not affect the rate of the average annual springflow.

Summary

During the period from April 2010 to May 2019 streamflow measurements from 02011799 Jackson River above spring near Hot Springs, Virginia and 02011800 Jackson River below Gathright Dam near Hot Springs Va., were used to determine the flow of a midchannel spring at the request of the U.S. Army Corps of Engineers Norfolk District. The calculated springflow data were analyzed to determine if correlations could be established between the elevation of Lake Moomaw or local precipitation data from Hot Springs, Va., and were evaluated for trends over time. Results of these analyses indicated no direct correlations between springflow and lake elevation. The local precipitation data indicated that the amount of springflow did not respond to changes in recent or long-term precipitation totals based on the observed springflow values. Annual average springflow data were used to review trends over time, and the data showed little variation in flow over the study period.