The Cuddapah sedimentary basin extends over a significant part of the southern part of Andhra Pradesh State, Southern India. Proterozoic carbonate rocks in the basin are constituted by as three main units- the Vempalle dolomite, the Narji and Koilkuntla limestones. These carbonate rocks are of strategic im­portance for local communities as they provide the main water source for irrigation and domestic use and they are also inten­sively quarried for cement production and building stones. It is therefore, of primary importance to assess to which extent these carbonate units are karstified so as to provide recommendations for appropriate land and water resource management. The field investigations carried out indicate that these carbonate units are significantly karstified and karstification has been an ongo­ing process with several phases under variable climatic condi­tions. As a result, a significant part of aquifer recharge occurs as point-recharge through swallow-holes and groundwater flow is channelized by conduit networks which emerge at karst springs. Karst development was possibly more active during past humid conditions; however karstification is still an ongoing process under the present semi-arid climate especially in the favorable case where karst drains the runoff issued from upstream quartz­itic hills. The karstic nature of these carbonate units need to be integrated in future research and development programmes to avoid practices that may lead to unexpected collapses, reservoir leaks, inaccurate groundwater budgeting, etc.

The temporal budgets of the input, retainment and use by invertebrates of detritus and root tufts were evaluated in a short tropical limestone cave (337 m long). Detritus penetrate only through the stream in lower quantities in the dry season, contrary to what happens in the rainy season. However, water transport energies in the rainy season prevent detritus retainment. Roots tufts that emerge from the bottom of the stream provide shelter and food for several species. The abundance (log10) (R2 = 0.63; P < 0.02) and richness (log10) (R2 = 0.63; P < 0.01) related positively with the root tuft biomass (log10). In the terrestrial environment (ground), guano is the main secondary resource available for the invertebrates; the constant production of this resource has shown to influence the structure and distribution of invertebrates. Unfavorable temperature conditions and, especially low soil moisture, promote low plant detritus consumption rates. Historically, different authors assumed that organic resources imported by water are more available in caves in rainy seasons. It is clear that the importation of organic detritus in the rainy season is higher than in the dry season, but as shown in this work, the stochastic pulse flows continually disturb and remove the previously accumulated resource. So, the food that is truly used by the cave communities is that transported at the end of the rainy season (and during all the dry season) that becomes available for the cave fauna. The cave functionality depends, so, directly of the epigean food resources.

The Balcones Fault Zone Edwards aquifer (Edwards aquifer) is one of the major regional karst aquifers in the United States, with an average withdrawal of 950 million liters per day (L/d). This study focuses on the connection between the Uvalde pool and the San Antonio pool of the Edwards aquifer, west of the San Antonio metropolitan area in Uvalde County, Texas. This area is known as the Knippa Gap and is located north of the community of Knippa. The Knippa Gap is a major zone controlling the flow from the Uvalde pool to the San Antonio pool. The San Antonio pool is the primary source of water for the greater San Antonio water supply. The Knippa Gap is a restriction where the aquifer narrows to a width estimated to be approximately 4 km, is bounded by northeast trending faults of the Balcones Fault Zone on the north, and uplift from the Uvalde salient and igneous intrusive plugs to the south. (Green et al., 2006). The hydrogeology in the Knippa Gap has been a topic of major interest among researchers in this area for numerous years, yet the exact location, nature of boundaries, and karst hydrogeology are not well defined, and the flow through this area is in need of refinement to improve the aquifer water balance.
This study integrates recent research by other scientists with field studies conducted during the summer of 2012 as part of an M.S. thesis. This paper is limited to a discussion of the water quality as it relates to the southern flow boundary of the Knippa Gap near the Devils River Trend of the Uvalde salient. Water-quality data constrain a revised conceptual model of the flow and karstification in this critical area of recharge to the San Antonio pool, and provide specific lateral boundaries and vertical karstification zones which are being tested in the more comprehensive M.S. thesis. Although current interpretations are tentative, it appears this conceptual model will be readily convertible into a digital model that can test 2hypotheses relating a much broader suite of calibration data, including water levels, water budgets, and spring discharges.

Middle Triassic fractured and karstified limestone and dolomite form a karst aquifer in the Sana River Valley near the town of Prijedor. As a result of intensive tectonic movements, carbonate rocks are mostly below the Sana River level, covered by younger Pliocene and alluvial deposits. The main source of groundwater recharge is infiltration from the Sana River through its alluvium over most of the aquifer. The main objective of the research reported in this paper was to evaluate the hydraulic relationships of the alluvial, Pliocene and karst aquifers in order to better understand the water supply potential of the karst aquifer. Although the use of hydrodynamic modeling is not very common with karst aquifers, the developed model provided significant and useful information on the groundwater budget and recharge type. The influence of fault zones and spatial anisotropy of the karst aquifer were simulated on the hydrodynamic model by varying permeability on the xand y­axes of the Cartesian coordinate system with respect to the fault, the main pathway of groundwater circulation. Representative hydraulic conductivities were Kx

 = 2.3·10­3

 m/s and Ky

 = 5.0·10­3

 m/s in the faults of Nw to SE direction, and Kx

 = 2.5·10­3

 m/s and Ky

 1.2·10­3

 m/s in the faults of Sw to NE trend. Model research showed that the karst aquifer can be used in the long term at maximal tested capacities and that current groundwater exploitation is not compromised in dry periods when the water budget depends entirely on recharge from the Sana River.

Extensive research has been conducted investigating the relationship between karst processes, carbonate deposition and the global carbon cycle. However, little work has been done looking into the relationship between glaciations, subsequent sea level changes, and aerially exposed land masses in relation to karstic processes and the global carbon budget. During glaciations sea-level exposed the world’s carbonate platforms. with the sub-aerial exposure of the platforms, karst processes can occur, and the dissolution of carbonate material can commence, resulting in the drawdown of CO2 from the atmosphere as HCO3−. Furthermore, the material on the platform surfaces is primarily aragonite which is more readily soluble than calcite allowing karst processes to occur more quickly. During glaciations arctic carbonates and some of the temperate carbonates are blanketed in ice, effectively removing those areas from karst processes. Given the higher solubility of aragonite, and the extent of carbonate platforms exposed during glaciations, this dissolution balances the CO2 no longer taken up by karst processes at higher latitudes that were covered during the last glacial maximum The balance is within 0.001 GtC / yr, using soil pCO2 (0.005 GtC / yr assuming atmospheric pCO2) which is a difference of <1% of the total amount of atmospheric CO2 removed in a year by karst processes. Denudation was calculated using the maximum potential dissolution formulas of Gombert (2002). On a year to year basis the net amount of atmospheric carbon removed through karstic processes is equivalent between the last glacial maximum and the present day, however, the earth has spent more time in a glacial configuration during the quaternary, which suggests that there is a net drawdown of atmospheric carbon during glaciations from karst processes, which may serve as a feedback to prolong glacial episodes. This research has significance for understanding the global carbon budget during the quaternary.

An efficient conveyance system for groundwater is shown to have formed in a carbonate aquifer even though it is situated in a semi-arid environment. This conveyance system comprises preferential flow pathways that developed coincident with river channels. A strong correlation between high capacity wells and proximity to higher-order river channels (i.e., within 2.5 km) is used as evidence of preferential flow pathways. Factors that contributed to development of the preferential flow paths: (i) karst development in carbonate rocks, (ii) structural exhumation of a carbonate plateau, and (iii) the requirement that the groundwater regime of the watershed has adequate capacity to convey sufficient quantities of water at the required rates across the full extent of the watershed. Recognition of these preferential pathways in proximity to river channels provides a basis to locate where high capacity wells are likely (and unlikely) and indicates that groundwater flow within the watershed is relatively rapid, consistent with flow rates representative of karstic aquifers. This understanding provides a basis for better informed decisions regarding water-resource management of a carbonate aquifer in a semi-arid environment.