Spinal cord degeneration in a case of "recovered" spinal decompression sickness.

Degeneration in the spinal cord of goats after experimental decompression sickness is well documented but opportunities to examine the long-term effects in man are rare. We describe severe damage in the spinal cord of a man who had made an almost complete functional recovery from spinal decompression sickness

Myelopathy associated with decompression sickness: A report of six cases

Four scuba divers and 2 professional deep sea divers developed spinal cord symptoms due to decompression sickness. Symptoms developed during or immediately after ascent in 4 cases and were delayed in 2. In 2 cases new symptoms appeared during a jet flight. In 4 cases paraparesis was associated with a sensory level in the mid or low dorsal region indicating the thoracic cord as the major site of involvement. In the other 2 cases the clinical findings were suggestive of combined lesions in the lower cervical and lumbar cord. Therapeutic recompression led to improvement in each case. Three cases who were re-examined after intervals of 3 to 7 years each showed residual corticospinal and minor sensory signs. One of these cases met with a violent death 3.5 years after the acute episode; examination of the cord showed multifocal white matter degeneration in the posterior and lateral columns between C7 and T4 with secondary ascending and descending tract degeneration. The mechanism of spinal cord damage in decompression sickness is discussed

Hydrologic investigations of surface water groundwater interactions in a sub-catchment in the Namoi Valley, NSW, Australia.

In catchments with multiple inputs and outputs of water it can be difficult to reconcile why various reaches of a river are gaining or losing water. If rivers and adjacent aquifers are to be managed sustainably, while balancing environmental, economic and social goals, it is important that the link between the river and the aquifer is correctly characterised. This paper demonstrates how the joint analysis of rainfall, streamflow and borehole hydrograph data can contribute to elucidating the hydrological processes occurring in the catchment and hence understanding these links. In particular, the impact of the groundwater abstractions are examined by analysing the hydrological data over large time scales (decades) which span the pre- and post-irrigation development periods as well as short time scales (weeks) during pumping and flooding events

River–aquifer interactions in a semi-arid environment stressed by groundwater abstraction

Rivers and aquifers are, in many cases, a connected resource and as such the interactions between them need to be understood and quantified for the resource to be managed appropriately. The objective of this paper is to advance the understanding of river– aquifer interactions processes in semi-arid environments stressed by groundwater abstraction. This is performed using data from a specific catchment where records of precipitation, evapotranspiration, river flow, groundwater levels and groundwater abstraction are analysed using basic statistics, hydrograph analysis and a simple mathematical model to determine the processes causing the spatial and temporal changes in river–aquifer interactions. This combined approach provides a novel but simple methodology to analyse river–aquifer interactions, which can be applied to catchments worldwide. The analysis revealed that the groundwater levels have declined (~ 3 m) since the onset of groundwater abstraction. The decline is predominantly due to the abstraction rather than climatic changes (r = 0.84 for the relationship between groundwater abstraction and groundwater levels; r = 0.92 for the relationship between decline in groundwater levels and magnitude of seasonal drawdown). It is then demonstrated that, since the onset of abstraction, the river has changed from being gaining to losing during low-flow periods, defined as periods with flow less than 0.5, 1.0 or 1.5GL/day (1 GL/day = 1106m3/day). If defined as10 years) between the onset of groundwater abstraction and the changeover from gaining to losing conditions. Finally, a relationship between the groundwater gradient towards the river and the river flow at low-flow is demonstrated. The results have important implications for water management as well as water ecology and quality

Using groundwater modelling to enhance the understanding of the Maules Creek alluvial aquifer, Upper Namoi, NSW.

A groundwater flow model was developed for the Maules Creek alluvial aquifer, in the Namoi Valley (NSW, Australia). The objectives were to provide a better understanding of the dynamics of the aquifer and to provide integrated modelling of the catchment water resources, including an assessment of groundwater abstraction. The model was developed using FEFLOW 5.4. The hydrogeological system is represented by 9 layers bounded by impermeable bedrock. The hydraulic conductivity distribution in the model was based on a 3D geologic model built with EarthVision® and Mathematica™ using bore logs from the area. Hydrologic stresses include diffuse recharge, irrigation recharge, stream-aquifer interaction, lateral groundwater inflow/outflow and groundwater pumping. The hydraulic head distribution for 1978, obtained from a steady state model, was used as the initial condition for the transient model which was run from January 1978 to April 2007. Model calibration was performed by a trial-and-error method based on matching modelled bore hydrographs with measured hydrographs. Overall the model performance is good with the model correctly capturing the recovered water levels after each irrigation season, as well as the long-term trends. However, in areas with large groundwater abstraction-induced drawdowns (up to 8-10 m) the seasonal dynamics are not captured well by the model. For assessing the effect of groundwater abstraction on stream-aquifer interactions, two scenarios were run: without groundwater pumping and with a 2-fold increase in the pumping rate. The baseflow fluxes to the river and water budgets were computed for each scenario and compared with the calibration scenario. The groundwater model has provided a better understanding of the alluvial aquifer system and its dynamics. The results show the impact of irrigation on the hydraulic head distribution and baseflow to the river. Limitations and possible methods of resolving model uncertainties and improving calibration performance were also investigated