Research about Keystone Lake

USGS2024

Using down-scan capabilities from recreational-grade side-scan sonar systems to sample paddlefish and evaluate depth use in a reservoir

Recreational-grade side-scan sonar (SSS) has only recently been applied to estimate abundance of Paddlefish Polyodon spathula , a large pelagic planktivore, in reservoirs. Current recreational-grade SSS units also have a dedicated down-scan channel, which may be useful for detecting Paddlefish in reservoirs because the range of depths they inhabit. We investigated the utility of down-scan images using SSS data from a previously published study of Paddlefish in Keystone Lake, Oklahoma. Two readers counted Paddlefish and estimated the depth of each fish and the water column. We used proximity functions in a geographic information system to find individual Paddlefish that were common between the readers. We further used proximity functions to identify common fish observed from the SSS survey conducted previously as an aid to compare and refine down-scan estimates. Depth of Paddlefish averaged approximately 7 m, but fish were deeper when water was deeper. Density estimates from down-scan were comparable to side-scan, but only after utilizing the side-scan data to adjust for detection-by-distance in a dual-gear approach. Down-scan data thus appear to be useful for not only estimating density of Paddlefish, but also for incorporating depth use, creating a three-dimensional database of locations that can inform managers of optimal depths for sampling gear (e.g., gill nets), improve monitoring efficiency, and facilitate better management of reservoir populations.

Oklahoma↗

USGS1976

A hydrologic description of Keystone Lake near Tampa, Florida

The terrain around Keystone Lake, a 388-acre lake in northwest Hillsborough County, Florida, near the Cosme well field, is dotted with sinks that promote leakage from the surficial aquifer to the underlying Floridan aquifer. The lake, an integral part of the Brooker Creek channel, receives overland runoff from cypress swamps, pastures, citrus groves, and lakefront residential areas. The lake, a composite of many coalescing sinkholes, is generally 14 to 16 ft deep and has been dredged in places to 23 ft deep. Since 1960, rainfall in the area shows a cumulative negative departure of 86 in. from the long-term average. The mean annual lake stage in 1973 was the lowest on record. Concurrently, municipal pumpage in the Cosme well field from the Floridan aquifer peaked in 1961 and again in 1973, and in 1972 the potentiometric surface was the lowest since 1960. Comparisons of the hydrographs of lake stage and the potentiometric surface in the Floridan aquifer with rainfall graphs shows that both correspond closely to seasonal rainfall, resulting in the trend of decreasing seasonal maximum levels in the lake and the aquifer. Keystone Lake water quality is adequate for recreation and propagation of wildlife. (Woodard-USGS)

Florida↗