Mass Flux of Agricultural Nonpoint-Source Pollutants in a Conduit-Flow-Dominated Karst Aquifer, Logan County, Kentucky

Changes in water quality in a karst ground-water basin used intensively for agriculture are being measured before, during, and after the implementation of best management practices (BMP’s) and other management practices, to determine the success of such programs in protecting ground water. The study was divided into three phases. The results of the first two phases are included in this report and cover research conducted between August 1990 and October 1994. During phase I of the study the overall ground-water quality of the basin and its hydrogeology were investigated. Phase II began monitoring the water quality at Pleasant Grove Spring before BMP implementation. The Pleasant Grove Spring Basin in southern Logan County, Ky., was selected for study because it is largely free of nonagricultural pollution sources. About 70 percent of the watershed is in crop production and 22 percent is pasture. The area of the karst drainage basin is approximately 10,054 acres (4,069 hectares), as determined by ground-water dye tracing. Ground-water flow in the basin is divided into a diffuse (slow) flow regime and a conduit (fast) flow regime. The diffuse and conduit flow regimes have a major influence on the timing of contaminant peaks and valleys during storms. Nitrate is the most widespread, persistent contaminant in the basin, but concentrations average 5.2 mg/L basinwide and generally do not exceed maximum contaminant levels (MCL’s) set by the U.S. Environmental Protection Agency for drinking water. Atrazine has been consistently detected in low concentrations, and other pesticides occasionally are detected. Concentrations of triazines (including atrazine) and alachlor have exceeded drinking-water MCL’s during spring flooding. Maximum concentrations of triazines, carbofuran, metolachlor, and alachlor in samples from Pleasant Grove Spring were 44.0, 7.4, 9.6, and 6.1 µg/L, respectively. Flow-weighted average concentrations for 1992–93 were 4.91 µg/L for atrazine-equivalent triazines and 5.0 mg/L for nitrate-nitrogen. Averages for 1993–94 were 0.97 µg/L and 5.7 mg/L, respectively. The difference in atrazine-equivalent triazine concentration between the 2 years may be either the result of weather conditions or crop patterns. Bacteria counts always exceed standards for drinking water and occasionally exceed standards for drinking-water supplies. Basinwide, samples averaged 465 fecal coliform colony-forming units per 100 ml (col/100 ml) and 1,891 fecal streptococci col/100 ml; maximum counts were 14,000 and 24,000 col/100 ml, respectively. Bacteriological speciation failed to identify the source of high bacteria counts at Pleasant Grove Spring, but showed that the bacteria are not indigenous to the natural environment of the basin. Suspended sediment discharging from Pleasant Grove Spring has had an adverse impact on aquatic biota downstream. In the Pleasant Grove Spring Basin, ground water for human consumption is adversely affected by contamination from triazines and bacteria. Implemented BMP’s should focus on reduction of runoff, disposal of animal waste, and efficient application of nutrients. A public education program on ground-water protection would also be beneficial

Generalized Block Diagram of the Western Pennyroyal Karst

Karst occurs where limestone or other soluble bedrock is near the earth\u27s surface, and fractures in the rock become enlarged when the rock dissolves. Sinkholes and sinking streams are two surface features that indicate karst development. In karst areas most rainfall sinks underground, resulting in fewer streams flowing on the surface than in non-karst settings. Instead of flowing on the surface, the water flows underground through caves, sometimes reemerging at karst windows, then sinks again to eventually discharge at a base-level spring along a major stream or at the top of an impermeable strata. The development of karst features is influenced by the type of soluble rock and how it has been broken or folded by geologic forces. There are four major karst regions in Kentucky: the Inner Bluegrass, Western Pennyroyal, Eastern Pennyroyal, and Pine Mountain. This diagram depicts the Western Pennyroyal karst

Kentucky Geological Survey Procedures for Groundwater Tracing Using Fluorescent Dyes

Karst terrain often develops from an ancestral landscape of surface-flowing streams, which leaves behind a relict pattern of the surface watershed divides. If caves only developed in ancestral watersheds, then groundwater tracing, for the purpose of groundwater basin mapping, would be unnecessary. But lithologic, structural, and hydrologic factors conspire to ensure that some caves extend headward faster than their neighbors and encroach upon adjacent groundwater basins to pirate drainage under the original surface divides. In many areas, groundwater basin boundaries have been significantly reorganized, to the point that there is little relationship to the ancestral surface watershed boundaries

Generalized Block Diagram of the Inner Bluegrass Karst

Karst occurs where limestone or other soluble bedrock is near the earth\u27s surface, and fractures in the rock become enlarged when the rock dissolves. Sinkholes and sinking streams are two surface features that indicate karst development. In karst areas most rainfall sinks underground, resulting in fewer streams flowing on the surface than in non-karst settings. Instead of flowing on the surface, the water flows underground through caves, sometimes reemerging at karst windows, then sinks again to eventually discharge at a base-level spring along a major stream or at the top of an impermeable strata. The development of karst features is influenced by the type of soluble rock and how it has been broken or folded by geologic forces. There are four major karst regions in Kentucky: the Inner Bluegrass, Western Pennyroyal, Eastern Pennyroyal, and Pine Mountain. This diagram depicts the Inner Bluegrass karst

Characteristics of Cover-Collapse Sinkholes in Kentucky

Sudden collapse of unconsolidated earth materials over soluble bedrock, known as cover collapse, damages buildings, roads, utility lines, and farm equipment in Kentucky. It has also killed livestock, including Thoroughbred horses, and injured people. The estimated annual cost of sinkhole cover collapse in Kentucky ranges from $20 million to$84 million and is sensitive to rare but expensive events such as the 2014 National Corvette Museum collapse. The Kentucky Geological Survey began developing a catalog of case histories of cover-collapse occurrences in 1997, and receives an average of 24 reports each year. Three hundred fifty-four occurrences of cover-collapse sinkholes throughout Kentucky are documented, and cover-collapse variables such as diameter, elongation, and depth as a function of bedrock type and time of year have been statistically analyzed. Statewide, cover-collapse sinkholes are on average 2.7 m long, 1.9 m wide, and 2.4 m deep. Some can be substantially larger and deeper. Data in the catalog show that new occurrences of cover collapse may initiate the formation of new sinkholes, but cover collapse generally does not occur in existing sinkholes. Historically, the number of collapses is smallest in February, steadily increases to peak in July, and then decreases through December and into January

Changes in Groundwater Quality in a Conduit-Flow-Dominated Karst Aquifer as a Result of Best Management Practices

Water quality in the Pleasant Grove Spring karst groundwater basin was monitored to determine the effectiveness of best management practices (BMP’s) implemented through the U.S. Department of Agriculture’s Water Quality Incentive Program (WQIP). The project was divided into three phases. Phase I, beginning in August 1990, was the initial reconnaissance of the hydrogeology and water quality of the basin. Phase II, beginning in October 1993, monitored the water quality for 1 year prior to BMP implementation. This phase was followed by a 1-year interim extension, which continued the monitoring. Phase III monitored the water quality during and following BMP implementation. The findings of phases I and II, along with extensive descriptions of the hydrogeology and groundwater quality, were reported in Currens (1999). This report covers the specific findings of the interim extension and phase III (October 1994–October 1998). It also summarizes the overall findings of the project and evaluates the outcome of the BMP’s, which began in 1995. Pleasant Grove Spring discharges runoff from a 4,069-hectare (10,054-acre) karst groundwater basin in southern Logan County, southwestern Kentucky. The basin is characterized by mature karst topography developed on Mississippian carbonates mantled with residuum. Sinkholes and sinking streams dominate the landscape, and perennial surface-flowing streams occur only in the headwaters of the basin. Most of the area of the basin (about 90 percent) is used for agriculture. The principal crop grown is corn in rotation with winter wheat and soybeans. Other row crops include tobacco and other small grains. Livestock are dairy and beef cattle and swine. Over 68 percent of the area of the watershed was enrolled in the WQIP. Analysis of samples collected since October 1994 at seven locations in the basin indicated the principal contaminants of probable agricultural origin were herbicides, nitrate-nitrogen, suspended sediment, orthophosphate, and bacteria (as was the case during the first two phases of the project). The maximum nitrate-nitrogen concentration measured in the basin between 1994 and 1998 was 13.1 mg/L, at Leslie Page karst window, and the average concentration was 5.05 mg/L. The maximum orthophosphate concentration was 1.4 mg/L, at Pleasant Grove Spring, and the median was 0.17 mg/L. The total suspended solids maximum was 3,267 mg/L, and the median concentration was 53 mg/L. The maximum triazine concentration measured by enzyme-linked immunosorbent assay (ELISA) was 393.0 µg/L, at Leslie Page karst window; median concentration was 1.15 µg/L. Maximum bacteria counts were 200,000 fecal coliform colony-forming units per 100 mL (col/100 mL) and 810,000 fecal streptococci col/100 mL; medians were 400 col/100 mL and 640 col/100 mL, respectively. Water quality at Pleasant Grove Spring was monitored from May 1992 through the end of the project in October 1998. The maximum nitrate-nitrogen concentration measured at the spring was 8.11 mg/L, and the concentration never exceeded the maximum contaminant level (MCL) of 10 mg/L; average concentration was 4.8 mg/L. The maximum orthophosphate concentration was 1.4 mg/L and the median was 0.53 mg/L. The total suspended solids maximum was 3,073 mg/L, and median was 55 mg/L. The maximum triazine concentration (ELISA) was 62.2 µg/L. Triazine concentrations briefly exceed MCL’s during the spring each year. Peak concentrations of the other three frequently analyzed pesticides (alachlor, metolachlor, and carbofuran) were 12.0, 29.6, and 7.4 µg/L, respectively—the highest measured in the basin. Median concentrations of these pesticides, however, are near detection limits. Fecal coliform and fecal streptococci bacteria are always present at Pleasant Grove Spring, and counts occasionally exceed drinking-water supply limits (2,000 col/100 mL). Maximum bacteria counts were 60,000 col/100 mL of fecal coliform and 200,000 col/100 mL of fecal streptococci. The quality of groundwater discharging at Pleasant Grove Spring before and after BMP implementation was evaluated by comparing the annual mass flux of nitrate-nitrogen, total suspended solids, and triazines (atrazine-equivalent). Annual descriptive statistics were compared for orthophosphate and bacteria, as well as for the other contaminants. The flux and annual statistics of nitrate-nitrogen were little changed over the course of the BMP program. Atrazine-equivalent flux and triazine geometric averages indicated an increase. Total suspended solids concentrations decreased slightly, whereas orthophosphate increased slightly. Fecal streptococci counts improved, but the improvement was not statistically significant. The comparison of the pre- and post-BMP monitoring indicates that the WQIP was only partly successful. Although the program was fully implemented, the types of BMP’s funded and the rules for BMP participation resulted in less-effective BMP’s being chosen by producers. Future BMP programs for the protection of groundwater in karst aquifers should limit BMP’s to the installation of buffer strips around sinkholes, the exclusion of livestock from streams, and the removal of certain land from agricultural production

Model Ordinance for Development on Karst in Kentucky: Guidance for Construction on Karst Terrain and the Reduction of Property Damage and Threat to Human Health Resulting from Karst Geologic Hazard

I have dealt with hundreds of incidents of karst-related geohazards; some have caused major damage to buildings and infrastructure. Although cases are largely limited to the ground surface being made unusable, a significant number of structures are damaged by karst flooding or cover collapse each year, which is devastating to families who have lost their homes. Most of these events should never have happened, because the karst hazard could have been avoided by selecting a better building site or designing the building to withstand the damage from the hazard. Furthermore, most of the planning authorities I have had experience with seem uninformed about the potential consequences of construction on these areas. They need to know what to do to avoid karst geohazards and mitigate damage. As a result, this model ordinance has been prepared for use by local government bodies to provide them with a template of how to minimize damage from karst geohazards

Generalized Block Diagram of the Pine Mountain Karst

Karst occurs where limestone or other soluble bedrock is near the earth\u27s surface, and fractures in the rock become enlarged when the rock dissolves. Sinkholes and sinking streams are two surface features that indicate karst development. In karst areas most rainfall sinks underground, resulting in fewer streams flowing on the surface than in non-karst settings. Instead of flowing on the surface, the water flows underground through caves to eventually discharge at a base-level spring along a major stream or at the top of an impermeable strata. The development of karst features is influenced by the type of soluble rock and how it has been broken or folded by geologic forces. There are four major karst regions in Kentucky: the Inner Bluegrass, Western Pennyroyal, Easter Pennyroyal, and Pine Mountain. This diagram depicts the Pine Mountain karst in southeastern Kentucky

Generalized Block Diagram of the Eastern Pennyroyal Karst

Karst occurs where limestone or other soluble bedrock is near the earth\u27s surface, and fractures in the rock become enlarged when the rock dissolves. Sinkholes and sinking streams are two surface features that indicate karst development. In karst areas most rainfall sinks underground, resulting in fewer streams flowing on the surface than in non-caves, sometimes reemerging at karst windows, then sinks again to eventually discharge at a base-level spring along a major stream or at the top of an impermeable strata. The development of karst features is influenced by the type of soluble rock and how it has been broken or folded by geologic forces. There are four major karst regions in Kentucky: the Inner Bluegrass, Western Pennyroyal, Eastern Pennyroyal, and Pine Mountain. This diagram depicts the Eastern Pennyroyal karst