Recent advancements in supercapacitor technology

. Identifying areas of interaction between groundwater and surface water is crucial for effective environmental management, because this interaction is known to influence water quantity and quality. This paper applies hydrochemistry and multivariate statistics to identify locations and mechanisms of groundwater-surface water interaction in the pastorally dominated Wairarapa Valley, New Zealand. Hierarchical Cluster Analysis (HCA) and Principal Components Analysis (PCA) were conducted using site-specific median values of Ca, Mg, Na, K, HCO3, Cl, SO4 and electrical conductivity from 22 surface water sites and 246 groundwater sites. Surface water and groundwater monitoring sites were grouped together in three of the seven clusters identified by HCA, with the inference made that similarities in hydrochemistry indicate groundwater-surface water interaction. PCA indicated that the clusters were largely differentiated by total dissolved solids concentration, redox condition and ratio of major ions. Shallow aerobic groundwaters, located in close proximity to losing reaches of rivers, were grouped with similar Ca-HCO3 type surface waters, indicating potential recharge to aquifers from these river systems. Groundwaters that displayed a rainfall-recharged chemical signature with higher Na relative to Ca, higher Cl relative to HCO3 and an accumulation of NO3 were grouped with neighbouring surface waters, suggesting the provision of groundwater base flow to these river systems and the transfer of this chemical signature from underlying aquifers. The hydrochemical techniques used in this study did not reveal groundwater-surface water interaction in some parts of the study area, specifically where deep anoxic groundwaters, high in total dissolved solids with a distinct Na-Cl signature, showed no apparent link to surface water. The drivers of hydrochemistry inferred from HCA and PCA are consistent with previous measurements of 18O, water age and excess air. Overall, this study has shown that multivariate statistics can be used as a rapid method to identify groundwater-surface water interaction at a regional scale using existing hydrochemical datasets.

https://hess.copernicus.org/articles/15/3383/2011/hess-15-3383-2011.pdf

Regional-scale identification of groundwater-surface water interaction using hydrochemistry and multivariate statistical methods, Wairarapa Valley, New Zealand

Physical and chemical interactions between surface and groundwater are complex and display significant spatial and temporal variability. However, relatively little is known about the chemical interaction between surface and groundwater; in particular the temporal scales at which this interaction occurs. The aim of this research was to determine if existing and/or potential water chemistry measurements could be used to investigate the interaction between surface and groundwater bodies in the Wairarapa valley, New Zealand and identify specific locations and timescales at which this interaction occurs. Analyses were undertaken at both regional and local scales. The regional scale investigation utilised Hierarchical Cluster Analysis (HCA) to categorise 268 historic surface and groundwater sites from the 3000 km² Wairarapa valley into similar hydrochemical clusters in order to infer potential interaction. Six main clusters were identified, primarily differentiated by their total dissolved solids (TDS), redox potential and major ion ratios. Shallow aquifers, located in close proximity to losing reaches of the upper Ruamahanga, Waiopoua and Waiohine Rivers, were grouped with similar Ca²⁺-HCO₃⁻ type surface waters, indicating (potential) recharge from these river systems. Likewise, rainfall-recharged groundwater sites that displayed higher Na⁺ relative to Ca²⁺ and Cl⁻ relative to HCO₃⁻ were grouped with similar surface waters such as the Mangatarere and lower Waingawa streams. This suggests the provision of this rainfall-recharged signature to river base flow. Deep anoxic aquifers, high in TDS, were grouped together, but showed no statistical link to surface water sites. Results from the regional scale investigation highlight the potential use of HCA as a rapid and cost-effective method of identifying areas of surface and groundwater interaction using existing datasets. A local scale investigation utilised existing quarterly and monthly hydrochemical data from the Mangatarere and Waiohine Rivers and nearby groundwater wells in an attempt to gain insight into temporal variability in surface and groundwater interactions. Time series analysis and HCA were employed, however, the coarse time scales at which data was available made it difficult to make reliable inferences regarding this interaction. To overcome this issue, upstream and downstream surface and groundwater gauging stations were established in the Mangatarere Stream catchment for a 92 day period. Continuous electrical conductivity, water temperature and stage measurements were obtained at three of the four stations, along with one week of hydrochemical grab sampling. The fourth gauging station provided a more limited dataset due to technical issues. The downstream Mangatarere Stream received 30-60% of base flow from neighbouring groundwaters which provided cool Na⁺-Cl⁻ type waters, high in TDS and NO₃‾ concentrations. This reach also lost water to underlying groundwaters during an extended dry period when precipitation and regional groundwater stage was low. The upstream groundwater station received recharge primarily from precipitation as indicated by a Na⁺-Cl⁻-NO₃‾ signature, the result of precipitation passage through the soil-water zone. However, it appeared 2-4 m³/s of river recharge was also provided to the upstream groundwater station by the Mangatarere stream during an extended storm event on JD021-028. Mangatarere surface waters transferred a diurnal water temperature pattern and dilute Na⁺-Ca²⁺-Mg²⁺-HCO₃⁻-Cl⁻ signature to the upstream groundwater station on JD026-028. Results obtained from the Mangatarere catchment confirm the temporal complexities of ground and surface water interaction and highlight the importance of meteorological processes in influencing this interaction.

Groundwater and Surface Water Interaction, Wairarapa Valley, New Zealand

This study constitutes the first attempt to examine the microbial diversity in New Zealand groundwater samples using a culture‐ and cloning‐independent technique. In this investigation, 18 distinct terminal restriction fragment length polymorphism (T‐RFLP) peak profiles were generated from groundwater samples collected from various sites and aquifers in the Hutt Valley and the Wairarapa. Most peak profiles were similar, implying only small differences in microbial community structure in the groundwater samples collected, and relatively low microbial diversity compared to non‐aquifer water samples. Nonetheless, subtle but systematic differences in T‐RFLP peak profiles were observed between the aquifers and, in some instances, for groundwater samples collected at different locations within a single aquifer. Differences in the peak profiles appeared to be related to groundwater chemistry, particularly to concentrations of iron, manganese, nitrogen, and sulfur.

https://www.tandfonline.com/doi/pdf/10.1080/00288330.2006.9517405

Molecular analysis of bacterial communities in groundwaters from selected wells in the Hutt Valley and the Wairarapa, New Zealand

Groundwater age or residence time is the time water has resided in the subsurface since recharge. Depending on the application, this definition may or may not include travel through the unsaturated zone. The determination of groundwater age can aid understanding and characterization of groundwater resources, because it can provide information on e.g. groundwater mixing and flow, and volumes of groundwater and recharge. Groundwater age can be inferred from environmental tracers, such as SF₆ and tritium, that have a known input to groundwater and/or undergo known alteration processes in groundwater. The currently used age tracers face limitations regarding their application range and reliability. For example, some age tracers have local sources that can lead to contamination of groundwater. This contamination can result in misleading estimates of age. Other tracers have ambiguous inputs to groundwater, which can result in ambiguous age estimations. To reduce these limitations, it is now recognized that multiple tracers should be applied complementarily. There is also a need for new groundwater age tracers and/or new groundwater dating techniques to supplement the existing ones. Cost-effective and easily applicable tracers/techniques are preferred, since most established groundwater dating techniques are very costly and/or complex. Commonly measured hydrochemistry parameters , such as the concentrations of major ions and pH, have been suggested as cost-effective and easily determinable potential age tracers. To date, the use of commonly measured hydrochemistry parameters as independent age tracer has only been demonstrated for water recharged weeks to months ago relying on seasonal changes. Other studies applied commonly measured hydrochemistry complementarily to established age tracers to better constrain groundwater age and/or better understand and predict anthropogenic effects on groundwater quality. Further study is needed to assess the extent to which commonly measured hydrochemistry can be used to reduce uncertainty in tracer-inferred age as well as the extent to which commonly measured hydrochemistry can be used to extrapolate tracer-inferred age.  In addition to tracer specific limitations, quantification of uncertainty and ambiguity is not standard in age modelling. Although a few studies have attempted to quantify uncertainty in age modelling with the aid of probabilistic approaches, their methods are often relatively complex and not transferrable to the many cases with little available data. Uncertainties in the tracer’s recharge estimate and identification of appropriate model components, such as the objective function, have not been considered. Studies in other areas of hydrological modelling, where probabilistic approaches are more commonly used, have highlighted the need for careful identification of model components.

Characterization of Groundwater with Complementary Age Tracers

http://www.gw.govt.nz/assets/council-publications/Groundwater%20Monitoring%20Technical%20Report.pdf

Groundwater monitoring technical report

The present invention generally relates to a support structure for Tidal Energy Converters (TECs), the support structure being for completely submerged deployment. A preferred support structure includes a single stanchion (4), extending in a first direction, and a cross arm (5), extending in a second direction perpendicular or substantially perpendicular to the first direction. The cross arm (5) is statically attached to the stanchion (4), and can support a plurality of TECs (3). A support structure also includes a support frame (7), which extends further in a third direction, perpendicular or substantially perpendicular to the first and second directions, than in the second direction. The support frame (7) is operable to anchor the support structure to a seabed.

Support structure for tidal energy converter system

A submerged support structure for Tidal Energy Converters (TECs), comprises a single column or stanchion 4 and a cross arm 5, statically attached to the stanchion and extending substantially perpendicular to the stanchion axis. A support frame 7 extends from the stanchion in a plane substantially perpendicular to the cross arm and is attachable to the sea bed. The support frame may include struts 10 connecting between the stanchion 4 and sleeves 9 which are attachable to piles 11 in the seabed. This may produce a bi-pod arrangement, which is able to efficiently resist the main forces due to hydrodynamic loading. The cross arm and other components may be streamlined to minimise loading and turbulence.

Andy Jones

Papers

Groundwater monitoring technical report

Support structure for tidal energy converter system

Tidal energy converter system