Jame, vrtače in razpoke na eogenem krasu na Floridi, prostorska analiza z orodji GIS

The correlation between surface and subsurface karst development was explored by comparing the directionality and spatial distribution of karstic depressions around twenty-two select caves in the eogenetic karst of Florida. Orientations of cave passages and major axes of depressions around cave centrelines imply varying degrees of correlation between them. Spatial distribution of karstic depressions was studied by standard deviational ellipses of sinkhole centroids and nearest neighbour orientations around caves using spatial statistics tools of ArcGIS. An overall analysis of the data shows close connections between some caves and the surrounding sinkholes in terms of their orientation and spatial distribution, suggesting the importance of fracture systems in the development of karst.Z analizo smeri in prostorske porazdelitve vrtač v okolici 22 izbranih jam na eogenem krasu na Floridi smo raziskovali povezavo med površinskim in podzemnim razvojem krasa. Primerjava smeri jamskih rovov in glavnih osi vrtač v okolici jam kaže na različno stopnjo povezave med njimi. Prostorsko porazdelitev vrtač smo raziskovali z orodji prostorske statistike v okolju ArcGIS, pri tem smo uporabili elipse standardnih odklonov centroidov vrtač in smeri osi vrtač, najbližjih sosedov izbranih jamskih rovov. Celotna analiza podatkov je pokazala tesno povezanost med nekaterimi jamami in okoliškimi vrtačami z vidika njihove orientacije in lege, kar kaže na pomen razpoklinskih sistemov za razvoj krasa

Land use changes and groundwater quality in Florida

Abstract Land use changes around 26 karstic cave–spring systems in Florida were evaluated using geographic information system. Located in the unconfined or semiconfined zones of the Floridan aquifer, some of the cave–spring systems are directly connected to the surficial land use processes by sinking streams, whereas others receiving diffuse recharge are still vulnerable to contamination due to a thin sandy cover overlying the aquifer. Comparison of nitrate-producing land use practices between 2004 and 2013–2014 shows increasing risks of groundwater contamination in the Floridan aquifer. Proliferation of septic systems and wastewater treatment sites due to growing residential areas, increased use of fertilizers for farming and landscaping stand out as major causes of nitrate overload in the both surface and groundwater

Karst features on the Withlacoochee River, near Valdosta, Georgia

The Withlacoochee River of South Georgia crosses an area of karst landscape before it flows south into the Suwannee River in Florida. This limestone karst is particularly well-developed ~5 km northwest of Valdosta Georgia. At this location the Withlacoochee River crosses an area of widespread sinkhole development. Some of these sinkholes occur directly in the riverbed. Field studies by both the USGS and by faculty at Valdosta State University have shown that during periods of intense drought the water in the Withlacoochee River is completely consumed as 100% of the water flows into the sinks. Additionally, a small segment of the downstream portion of the river reverses flow and flows north into the sink area. When the river is at drought conditions many karst features can be observed both in and near the dry Withlacoochee channel. These karst features include disappearing streams, solution cavities, whirlpools, sinkholes, and caves. This also provides an excellent opportunity to observe conventional stream landforms such as channel features, depositional features, and flow features. During periods of higher rainfall, the Withlacoochee will return to normal flow. The USGS has studied groundwater flow in this are and has found that significant and rapid communication exists between the river and the underlying aquifer systems, including the important Floridan Aquifer

The Role of Antecedent Groundwater Heads in Controlling Transient Aquifer Storage and Flood Peak Attenuation in Karst Watersheds

Transient storage of floodwaters in aquifers is known to attenuate peak flows in rivers and drive subsurface dissolution. Transient aquifer storage could be enhanced in watersheds overlying karst aquifers where caves facilitate surface and groundwater exchange. Few studies, however, have examined controls on, or magnitudes of, transient aquifer storage or flood peak attenuation in karstic watersheds. Here we evaluate flood peak attenuation with multiple linear regression analyses of 10 years of river and groundwater data from the Suwannee River, which flows over the karstic upper Floridan aquifer in north‐central Florida and experiences frequent flooding. Regressions show antecedent river stage exerts the dominant control on magnitudes of transient aquifer storage, with recharge and time to peak having secondary controls. Specifically, low antecedent stages result in larger magnitudes of transient aquifer storage and thus greater flood attenuation than conditions of elevated antecedent stage. These findings suggest subsurface weathering, including cave formation and enlargement, caused by transient aquifer storage could occur on a more frequent basis in aquifers where groundwater table elevation is lowered due to anthropogenic or climatic influences. Our work also shows that measures of groundwater table elevation prior to an event could be used to improve predictive flood models