scholarly journals Hydrological Characteristics of the Te Hapua Wetland Complex:The Potential Influence of Groundwater Level, Bore Abstraction and Climate Change on Wetland Surface Water Levels

2021 ◽  
Author(s):  
◽  
Craig Wayne Allen
Keyword(s):  
Climate Change ◽  
Surface Water ◽  
Groundwater Level ◽  
Hydrological Cycle ◽  
Shallow Groundwater ◽  
Water Levels ◽  
Groundwater Abstraction ◽  
Potential Threat ◽  
Through Flow ◽  
Future Viability

<p>Te Hapua is a complex of small, privately owned wetlands approximately 60 km northwest of Wellington. The wetlands represent a large portion of the region's remaining palustrine swamps, which have been reduced to just 1% of the pre-1900 expanse. Whilst many land owners have opted to protect wetlands on their land with covenants, questions have been raised regarding potential threats stemming from the wider region. Firstly, some regional groundwater level records have shown significant decline in the 10 to 25 years they have been monitored. The reason for this is unclear. Wetlands are commonly associated with groundwater discharge, so a decline in groundwater level could adversely affect wetland water input. Secondly, estimated groundwater resources are currently just 8% allocated, so there is potential for a 92% increase in groundwater abstraction from aquifers that underlie the wetlands. Finally, predictions of future climate change indicate changes in rainfall quantity and intensity. This would likely alter the hydrological cycle, impacting on rainfall dependant ecosystems such as wetlands as well as groundwater recharge. Whilst previous ecological surveys at Te Hapua provide valuable information on biodiversity and ecological threat, there has been no detailed study of the hydrology of the wetlands. An understanding of the relationship between the surface water of the wetlands and the aquifers that underlie the area is important when considering the future viability of the wetlands. This study aims to define the local hydrology and assess the potential threat of 'long term' groundwater level decline, increased groundwater abstraction and predicted climate change. Eleven months of water level data was supplied by Wellington Regional Council for three newly constructed Te Hapua wetland surface water and adjacent shallow groundwater monitoring sites. The data were analysed in terms of their relative water levels and response to rainfall. A basic water balance was calculated using the data from the monitoring sites and a GIS analysis of elevation data mapped the wetlands and their watersheds. A survey of 21 individual wetlands was carried out to gather water quality and water regime data to enable an assessment of wetland class. Historical groundwater level trends and geological records were analysed in the context of potential threat to the wetlands posed by a decline in groundwater level. Climate change predictions for the Kapiti Coast were reviewed and discussed in the context of possible changes to the hydrological cycle and to wetlands. Results from the wetland survey indicated that there are two distinct bands of wetlands at Te Hapua. Fens are found mostly in the eastern band and are more likely to be discharge wetlands, some of which are ephemeral. Swamps are found mostly in the western band and are more likely to be recharge wetlands. Dominant water input to fens is via local rainfall and local through-flow of shallow groundwater, especially from surrounding dunes. The eastern band of wetlands is typified by higher dunes and hence has greater input from shallow groundwater than wetlands in the western band. Dominant water input to swamps is via local rainfall, runoff, and through-flow from the immediate watershed and adjacent wetlands. Overall, the future viability of the Te Hapua wetland complex appears promising. Historical groundwater declines appear to be minimal and show signs of reversing. Abstraction from deep aquifers is not likely to impact on wetland water levels. Climate change is likely to have an impact on the hydrological cycle and may increase pressure on some areas, especially ephemeral wetlands. The effect of climate change on groundwater level is more difficult to forecast, but may lower water level in the long term.</p>

scholarly journals Hydrological Characteristics of the Te Hapua Wetland Complex:The Potential Influence of Groundwater Level, Bore Abstraction and Climate Change on Wetland Surface Water Levels

2021 ◽  
Author(s):  
◽  
Craig Wayne Allen
Keyword(s):  
Climate Change ◽  
Surface Water ◽  
Groundwater Level ◽  
Hydrological Cycle ◽  
Shallow Groundwater ◽  
Water Levels ◽  
Groundwater Abstraction ◽  
Potential Threat ◽  
Through Flow ◽  
Future Viability

<p>Te Hapua is a complex of small, privately owned wetlands approximately 60 km northwest of Wellington. The wetlands represent a large portion of the region's remaining palustrine swamps, which have been reduced to just 1% of the pre-1900 expanse. Whilst many land owners have opted to protect wetlands on their land with covenants, questions have been raised regarding potential threats stemming from the wider region. Firstly, some regional groundwater level records have shown significant decline in the 10 to 25 years they have been monitored. The reason for this is unclear. Wetlands are commonly associated with groundwater discharge, so a decline in groundwater level could adversely affect wetland water input. Secondly, estimated groundwater resources are currently just 8% allocated, so there is potential for a 92% increase in groundwater abstraction from aquifers that underlie the wetlands. Finally, predictions of future climate change indicate changes in rainfall quantity and intensity. This would likely alter the hydrological cycle, impacting on rainfall dependant ecosystems such as wetlands as well as groundwater recharge. Whilst previous ecological surveys at Te Hapua provide valuable information on biodiversity and ecological threat, there has been no detailed study of the hydrology of the wetlands. An understanding of the relationship between the surface water of the wetlands and the aquifers that underlie the area is important when considering the future viability of the wetlands. This study aims to define the local hydrology and assess the potential threat of 'long term' groundwater level decline, increased groundwater abstraction and predicted climate change. Eleven months of water level data was supplied by Wellington Regional Council for three newly constructed Te Hapua wetland surface water and adjacent shallow groundwater monitoring sites. The data were analysed in terms of their relative water levels and response to rainfall. A basic water balance was calculated using the data from the monitoring sites and a GIS analysis of elevation data mapped the wetlands and their watersheds. A survey of 21 individual wetlands was carried out to gather water quality and water regime data to enable an assessment of wetland class. Historical groundwater level trends and geological records were analysed in the context of potential threat to the wetlands posed by a decline in groundwater level. Climate change predictions for the Kapiti Coast were reviewed and discussed in the context of possible changes to the hydrological cycle and to wetlands. Results from the wetland survey indicated that there are two distinct bands of wetlands at Te Hapua. Fens are found mostly in the eastern band and are more likely to be discharge wetlands, some of which are ephemeral. Swamps are found mostly in the western band and are more likely to be recharge wetlands. Dominant water input to fens is via local rainfall and local through-flow of shallow groundwater, especially from surrounding dunes. The eastern band of wetlands is typified by higher dunes and hence has greater input from shallow groundwater than wetlands in the western band. Dominant water input to swamps is via local rainfall, runoff, and through-flow from the immediate watershed and adjacent wetlands. Overall, the future viability of the Te Hapua wetland complex appears promising. Historical groundwater declines appear to be minimal and show signs of reversing. Abstraction from deep aquifers is not likely to impact on wetland water levels. Climate change is likely to have an impact on the hydrological cycle and may increase pressure on some areas, especially ephemeral wetlands. The effect of climate change on groundwater level is more difficult to forecast, but may lower water level in the long term.</p>

scholarly journals Delineation of Hydraulic Flow Regime Areas Based on the Statistical Analysis of Semicentennial Shallow Groundwater Table Time Series

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 828 ◽  
Author(s):  
Tamás Garamhegyi ◽  
István Gábor Hatvani ◽  
József Szalai ◽  
József Kovács
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Groundwater Level ◽  
Flow System ◽  
Shallow Groundwater ◽  
Water Levels ◽  
Discharge Zone ◽  
Long Term Changes ◽  
Shallow Groundwater Level

Shallow groundwater acts as an important source of water for the ecosystem, agriculture, drinking water supply, etc.; it is, however, among those water resources most sensitive to climate change, and especially to aridification. In the present study, the delineation of regional recharge and discharge zones of the Danube–Tisza Interfluve (Hungary, 8000 km2) is presented via the combination of multivariate time series and geomathematical methods to explore the subregions most sensitive to dewatering. The shallow groundwater level time series of 190 wells, covering a semicentennial period (1961 to 2010), were grouped into three validated clusters representing characteristically different subregions. Then, the subregions’ means and individual shallow groundwater level time series were investigated for long-term trends and compared with local meteorological variability (precipitation, evapotranspiration, etc.) to determine their regime characteristics. As a result, shallow recharge and discharge zones, a gravity-driven flow system, and the discharge zone of a deeper, overpressured flow system could be discerned with distinctive long-term changes in water levels. The semicentennial trends in shallow groundwater levels were significant (p < 0.05) in the recharge (−0.042 m y−1) and in the overpressured discharge zone (0.009 m y−1), and insignificant in the rest of the area (−0.005 m yr−1). The present results concur with previous findings from the area but provide a statistically sound and reproducible delineation of the regime areas on a much finer scale than before. With the determination of the different climatic processes driving the semicentennial trends prevailing in the shallow groundwater, the high vulnerability of the recharge zone is underlined, while the outlined overpressured flow system seems to act independently from semicentennial precipitation trends. This study provides a more in-depth picture of the long-term changes in shallow groundwater and its drivers in of one of the most important agricultural areas in Hungary. It outlines, in a generally applicable way, the most vulnerable subareas for irrigation relaying on shallow groundwater extraction. In addition, the results can help adaptation-strategy decision makers to initiate a more effective and area-focused intervention in the case of the predicted negative trends for vulnerable recharge areas under various climate change scenarios.

scholarly journals Transient flow between aquifers and surface water: analytically derived field-scale hydraulic heads and fluxes

2012 ◽  
Vol 16 (3) ◽  
pp. 649-669 ◽  
Author(s):  
G. H. de Rooij
Keyword(s):  
Surface Water ◽  
Transient Flow ◽  
Hydrological Cycle ◽  
Realistic Model ◽  
Water Levels ◽  
Subsurface Water ◽  
Water Model ◽  
Infinite Strip ◽  
Catchment Scale ◽  
Basin Scale

Abstract. The increasing importance of catchment-scale and basin-scale models of the hydrological cycle makes it desirable to have a simple, yet physically realistic model for lateral subsurface water flow. As a first building block towards such a model, analytical solutions are presented for horizontal groundwater flow to surface waters held at prescribed water levels for aquifers with parallel and radial flow. The solutions are valid for a wide array of initial and boundary conditions and additions or withdrawals of water, and can handle discharge into as well as lateral infiltration from the surface water. Expressions for the average hydraulic head, the flux to or from the surface water, and the aquifer-scale hydraulic conductivity are developed to provide output at the scale of the modelled system rather than just point-scale values. The upscaled conductivity is time-variant. It does not depend on the magnitude of the flux but is determined by medium properties as well as the external forcings that drive the flow. For the systems studied, with lateral travel distances not exceeding 10 m, the circular aquifers respond very differently from the infinite-strip aquifers. The modelled fluxes are sensitive to the magnitude of the storage coefficient. For phreatic aquifers a value of 0.2 is argued to be representative, but considerable variations are likely. The effect of varying distributions over the day of recharge damps out rapidly; a soil water model that can provide accurate daily totals is preferable over a less accurate model hat correctly estimates the timing of recharge peaks.

scholarly journals Deep Learning based assessment of groundwater level development in Germany until 2100

2021 ◽  
Author(s):  
Andreas Wunsch ◽  
Tanja Liesch ◽  
Stefan Broda
Keyword(s):  
Climate Change ◽  
Groundwater Level ◽  
Climate Models ◽  
Groundwater Resources ◽  
Groundwater Abstraction ◽  
Water Shortages ◽  
Entire Area ◽  
Groundwater Levels ◽  
The Past ◽  
Skill Scores

&lt;p&gt;Clear signs of climate stress on groundwater resources have been observed in recent years even in generally water-rich regions such as Germany. Severe droughts, resulting in decreased groundwater recharge, led to declining groundwater levels in many regions and even local drinking water shortages have occurred in past summers. We investigate how climate change will directly influence the groundwater resources in Germany until the year 2100. For this purpose, we use a machine learning groundwater level forecasting framework, based on Convolutional Neural Networks, which has already proven its suitability in modelling groundwater levels. We predict groundwater levels on more than 120 wells distributed over the entire area of Germany that showed strong reactions to meteorological signals in the past. The inputs are derived from the RCP8.5 scenario of six climate models, pre-selected and pre-processed by the German Meteorological Service, thus representing large parts of the range of the expected change in the next 80 years. Our models are based on precipitation and temperature and are carefully evaluated in the past and only wells with models reaching high forecasting skill scores are included in our study. We only consider natural climate change effects based on meteorological changes, while highly uncertain human factors, such as increased groundwater abstraction or irrigation effects, remain unconsidered due to a lack of reliable input data. We can show significant (p&lt;0.05) declining groundwater levels for a large majority of the considered wells, however, at the same time we interestingly observe the opposite behaviour for a small portion of the considered locations. Further, we show mostly strong increasing variability, thus an increasing number of extreme groundwater events. The spatial patterns of all observed changes reveal stronger decreasing groundwater levels especially in the northern and eastern part of Germany, emphasizing the already existing decreasing trends in these regions&lt;/p&gt;

scholarly journals Factors influencing surface water and groundwater interaction in alluvial fan

2020 ◽  
Author(s):  
Fanao Meng ◽  
Changlai Xiao ◽  
Xiujuan Liang ◽  
Ge Wang ◽  
Ying Sun ◽  
...  
Keyword(s):  
Surface Water ◽  
River Runoff ◽  
Groundwater Level ◽  
Alluvial Fan ◽  
Water Levels ◽  
Key Factors ◽  
Groundwater Exploitation ◽  
Factors Affecting ◽  
Surface Water And Groundwater ◽  
The Relationship

Abstract In this study, the surface water balance method was used to calculate the interaction between surface water and groundwater (SGW) in the Taoer River alluvial fan in Jilin Province, China, from 1956 to 2014. The automatic linear model was used to determine the key and non-key influencing factors, and correlation analysis was performed to evaluate their relationship with one another. River runoff and groundwater level were the key factors affecting the SGW interaction, and sand–gravel exposure in the fan was more conducive to SGW interaction. There was a positive correlation between runoff and SGW interaction, and the relationship between the groundwater and surface water levels was correlated and affected by groundwater exploitation and groundwater runoff. Groundwater exploitation and evaporation and precipitation indirectly influenced the SGW interaction by affecting the groundwater level and river runoff key factors, respectively, and were considered non-key factors.

scholarly journals Evaluation of impacts of future climate change and water use scenarios on regional hydrology

2018 ◽  
Vol 22 (9) ◽  
pp. 4793-4813 ◽  
Author(s):  
Seungwoo Chang ◽  
Wendy Graham ◽  
Jeffrey Geurink ◽  
Nisai Wanakule ◽  
Tirusew Asefa
Keyword(s):  
Climate Change ◽  
Surface Water ◽  
Water Use ◽  
Groundwater Level ◽  
Water Demand ◽  
Environmental Regulations ◽  
Hydrologic Model ◽  
Tampa Bay ◽  
Future Climate ◽  
Future Climate Change

Abstract. General circulation models (GCMs) have been widely used to simulate current and future climate at the global scale. However, the development of frameworks to apply GCMs to assess potential climate change impacts on regional hydrologic systems, ability to meet future water demand, and compliance with water resource regulations is more recent. In this study eight GCMs were bias-corrected and downscaled using the bias correction and stochastic analog (BCSA) downscaling method and then used, together with three ET0 methods and eight different water use scenarios, to drive an integrated hydrologic model previously developed for the Tampa Bay region in western central Florida. Variance-based sensitivity analysis showed that changes in projected streamflow were very sensitive to GCM selection, but relatively insensitive to ET0 method or water use scenario. Changes in projections of groundwater level were sensitive to both GCM and water use scenario, but relatively insensitive to ET0 method. Five of eight GCMs projected a decrease in streamflow and groundwater availability in the future regardless of water use scenario or ET method. For the business as usual water use scenario all eight GCMs indicated that, even with active water conservation programs, increases in public water demand projected for 2045 could not be met from ground and surface water supplies while achieving current groundwater level and surface water flow regulations. With adoption of 40 % wastewater reuse for public supply and active conservation four of the eight GCMs indicate that 2045 public water demand could be met while achieving current environmental regulations; however, drier climates would require a switch from groundwater to surface water use. These results indicate a high probability of a reduction in future freshwater supply in the Tampa Bay region if environmental regulations intended to protect current aquatic ecosystems do not adapt to the changing climate. Broad interpretation of the results of this study may be limited by the fact that all future water use scenarios assumed that increases in water demand would be the result of intensification of water use on existing agricultural, industrial, and urban lands. Future work should evaluate the impacts of a range of potential land use change scenarios, with associated water use change projections, over a larger number of GCMs.

scholarly journals Modeling groundwater responses to climate change in the Prairie Pothole Region

2020 ◽  
Vol 24 (2) ◽  
pp. 655-672 ◽  
Author(s):  
Zhe Zhang ◽  
Yanping Li ◽  
Michael Barlage ◽  
Fei Chen ◽  
Gonzalo Miguez-Macho ◽  
...  
Keyword(s):  
Climate Change ◽  
Hydrological Cycle ◽  
Prairie Pothole Region ◽  
Regional Scale ◽  
Shallow Groundwater ◽  
Snow Accumulation ◽  
Soil Freezing ◽  
Prairie Pothole ◽  
The Mean ◽  
Recharge Rates

Abstract. Shallow groundwater in the Prairie Pothole Region (PPR) is predominantly recharged by snowmelt in the spring and supplies water for evapotranspiration through the summer and fall. This two-way exchange is underrepresented in current land surface models. Furthermore, the impacts of climate change on the groundwater recharge rates are uncertain. In this paper, we use a coupled land–groundwater model to investigate the hydrological cycle of shallow groundwater in the PPR and study its response to climate change at the end of the 21st century. The results show that the model does a reasonably good job of simulating the timing of recharge. The mean water table depth (WTD) is well simulated, except for the fact that the model predicts a deep WTD in northwestern Alberta. The most significant change under future climate conditions occurs in the winter, when warmer temperatures change the rain/snow partitioning, delaying the time for snow accumulation/soil freezing while advancing early melting/thawing. Such changes lead to an earlier start to a longer recharge season but with lower recharge rates. Different signals are shown in the eastern and western PPR in the future summer, with reduced precipitation and drier soils in the east but little change in the west. The annual recharge increased by 25 % and 50 % in the eastern and western PPR, respectively. Additionally, we found that the mean and seasonal variation of the simulated WTD are sensitive to soil properties; thus, fine-scale soil information is needed to improve groundwater simulation on the regional scale.

scholarly journals A review on the driving forces of water decline and its impacts on the environment in Poyang Lake, China

2020 ◽  
Author(s):  
Qiyue Li ◽  
Geying Lai ◽  
Adam Thomas Devlin
Keyword(s):  
Climate Change ◽  
Migratory Birds ◽  
Driving Forces ◽  
Poyang Lake ◽  
Ecological Impacts ◽  
Water Levels ◽  
Sand Mining ◽  
Potential Threat ◽  
Lake Ecosystems ◽  
Natural Lakes

Abstract The recession of water levels of natural lakes and their associated impacts on wetland ecosystems is a serious issue worldwide. Poyang Lake (the largest freshwater lake in China) has experienced a heightened and prolonged water decline since the year 2000, which causes concern for associated ecological impacts. In particular, climate change, operation of the Three Gorges Dam (TGD), and high magnitude sand mining appear to be well-correlated with the occurrence of water decline in Poyang Lake. Though the above factors have been analyzed in previous studies, a comprehensive summary has never been compiled. This paper provides a detailed literary review highlighting the driving forces and possible impacts of the consistent water decline in Poyang Lake. We conclude here that the operation of TGD is a fundamental cause for the lake water decline, aggravated by climate change and sand mining. The water decline has caused a deterioration of water quality, as well as having given rise to a potential threat to the habitat of migratory birds and Yangtze finless porpoises. The paper intends to offer constructive references that can be used in decision-making for effective protection of water resources and lake ecosystems.

scholarly journals Statistical modeling of spatial and temporal vulnerability of groundwater level in the Gaza Strip (Palestine)

2021 ◽  
Author(s):  
Hassan Al-Najjar ◽  
Gokmen Ceribasi ◽  
Emrah Dogan ◽  
Khalid Qahman ◽  
Mazen Abualtayef ◽  
...  
Keyword(s):  
Climate Change ◽  
Groundwater Level ◽  
Climate Changes ◽  
Gaza Strip ◽  
Mean Square ◽  
Potential Evaporation ◽  
Groundwater Pumping ◽  
Groundwater Abstraction ◽  
Groundwater Balance ◽  
The Gaza Strip

Abstract The water supply in the Gaza Strip substantially depends on the groundwater resource of the Gaza coastal aquifer. The climate changes and the over-exploiting processes negatively impact the recovery of the groundwater balance. The climate variability is characterized by the decline in the precipitation by −5.2% and an increase in the temperature by +1 °C in the timeframe of 2020–2040. The potential evaporation and the sunshine period are expected to increase by about 111 mm and 5 hours, respectively, during the next 20 years. However, the atmosphere is predicted to be drier where the relative humidity will fall by a trend of −8% in 20 years. The groundwater abstraction is predicted to increase by 55% by 2040. The response of the groundwater level to climate change and groundwater pumping was evaluated using a model of a 20-neuron ANN with a performance of the correlation coefficient (r)=0.95–0.99 and the root mean square error (RMSE)=0.09–0.21. Nowadays, the model reveals that the groundwater level ranges between −0.38 and −18.5 m and by 2040 it is expected to reach −1.13 and −28 m below MSL at the northern and southern governorates of the Gaza Strip, respectively.

scholarly journals REAKCJA WÓD POWIERZCHNIOWYCH I PODZIEMNYCH NA OPADY W ZLEWNI RÓŻANEGO STRUMIENIA

1970 ◽  
pp. 7-19
Author(s):  
ALEKSANDRA CZUCHAJ ◽  
FILIP WOLNY ◽  
MAREK MARCINIAK
Keyword(s):  
Time Series ◽  
Surface Water ◽  
Water Level ◽  
Correlation Coefficient ◽  
Groundwater Level ◽  
Water Levels ◽  
Groundwater Levels

The aim of the presented research was to analyze the relation between three variables: the daily sum of precipitation, the surface water level and the groundwater level in the Różany Strumień basin located in Poznań, Poland. The correlation coefficient for the subsequent lags for each pair of variables time series has been calculated. The delay with which waters of the basin respond to precipitation varies significantly. Generally, stronger response to rainfall is observed for surface water levels as opposed to groundwater levels.

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