Relation between climate variability and groundwater levels in the upper carbonate aquifer, southern Manitoba, Canada

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Abstract

Modeled trends of key climate variables in the Winnipeg area show that the annual mean temperature has increased by about 1 °C over the past 105 years. Potential impacts of climate change on groundwater levels are investigated by analyzing the relationship between historical climate records and water levels in monitoring wells completed in the upper carbonate aquifer. Both precipitation and annual mean temperature display a strong correlation with annual groundwater levels in this aquifer. The correlation with temperature becomes stronger in the periods of higher annual mean temperatures. In areas where the aquifer is found at shallow depth, temperature has a greater influence than precipitation on groundwater levels. Results suggest that a trend of increasing temperatures, predicted by global climate models for this region, may reduce net recharge and affect groundwater levels.

Introduction

Climate trend analysis indicates that global mean surface temperature has increased by about 0.3–0.6 °C since the late 19th century (Nicholls et al., 1996), and on Canadian Prairies the mean temperature has increased 1 °C during the last century (Zhang et al., 2000, Gan, 1998). Predictions are that global surface temperature will increase a further 1.4–5.8 °C between 1990 and 2100 (Showstack, 2001), and 1–5 °C across Canada (for the years 2029–2049 scenario from the Canadian Global Climate Change Model I, Nyirfa and Harron, 2001). Although most global climate models do not predict significant changes in precipitation for Canada, a variable, but persistent trend of decreasing annual precipitation in the Canadian Prairies in the last 40 years has been observed (Gan, 1998). Studies suggest that climate change will lead to less surface water availability in the Canadian Prairies (Lewis, 1989, Schindler, 2001, Schindler et al., 1996), thus increasing the need for groundwater development.

Groundwater has been an important water supply for industrial, agricultural and residential use on the Canadian Prairies (Maathuis and Thorleifson, 2000, Betcher et al., 1995). Increasing demands raise concerns about maintaining a sustainable supply of groundwater for this region even under normal climate conditions. In order to plan for sustainable development, climate change impacts on groundwater supply also need to be considered.

Impacts of climate change on groundwater are poorly understood and the relationship between climate variables and groundwater is more complicated than that with surface water. Groundwater resources are related to climate change through hydrologic processes, such as precipitation and evapotranspiration, and through interaction with surface water (Hafmann et al., 2000, Freeze and Cherry, 1979, Hornberger et al., 1997). With increased evapotranspiration and decreased precipitation, the impact of climate change will result in declining groundwater levels, which would cause some wells to become dry while others would become less productive due to the loss of available drawdown (Hafmann et al., 2000). Anthropogenic processes such as the consumption of groundwater by pumping could worsen the situation. Long lasting severe dry weather conditions may even alter hydraulic properties of an aquifer, as observed in a regional karst aquifer in France (Larocque et al., 1998), thus significantly altering recharge rates for major aquifer systems and affecting the sustainable yield of ground water in the region. Climate change may also affect groundwater quality. For example, a decline in fresh groundwater level in the east and north of the Winnipeg region may disrupt the current balance of the freshwater/saline water boundary in the carbonate rock aquifer, resulting in a saline water intrusion (Grasby and Betcher, 2002).

Predicting the impacts of climate change and developing adaptation strategies are essential for ensuring a sustainable groundwater supply in this region. However, potential impacts are difficult to accurately assess, as the influence of climate change on groundwater levels cannot be detected immediately. Groundwater flow systems have deferring abilities to retain and transport water, and the residence times of groundwater could vary from days to tens of thousands of years. This is likely to delay and disperse the impacts of climate change (Hafmann et al., 2000). Although numerical modeling of groundwater response to climate change may be useful, quantitative information on hydraulic properties and their spatial characteristics required for groundwater modeling are poorly known for many of the major aquifers in this region.

In the Canadian Prairie provinces, however, groundwater monitoring networks are common and observations of key climatic variables are available from meteorological observation stations across the region. Previous studies in Canadian Prairies have shown that under natural conditions, annual groundwater level fluctuation and long-term trends depend on net groundwater recharge, which is a function of total precipitation and evapotranspiration (Rutulis, 1989). A more recent study in southern Manitoba also shows that climate trends have good correlations with groundwater level variations (Chen et al., 2002). By using principal component analysis as a tool, Winter et al. (2000) were able to relate typical hydrograph features either to groundwater recharge characteristics or to the effect of difference in geological properties. Similarly, the impact of climate variability on groundwater levels can be investigated by analyzing the relationship between historical climate records and groundwater level fluctuations. In this study, we examine the general trends of local climate variation in the Winnipeg area, analyze the relationship between these trends and groundwater level fluctuations, and discuss the potential impacts of climate change on groundwater recharge of the upper carbonate aquifer, one of the largest fresh water aquifers in Canada.

Section snippets

Methods

The relative importance of climate on groundwater level variation is examined by using cross-correlation analysis, which is defined asCxy(k)=1nt=1n−k(xtx̄)(yt+kȳ)rxy(k)=Cxy(k)σxσywhere Cxy(k) is the cross-correlogram, rxy(k) is the cross-correlation coefficient, and σx and σy are the standard deviations of the time series. Since groundwater level response to climate variation will display a time delay which is difficult to determine, an apparent time delay is defined as the time shift, in

Regional hydrogeological setting

The carbonate rock aquifer occurs along the eastern edge of the Williston Basin in southern Manitoba. The aquifer is formed by a series of gently west dipping Middle Ordovician to Middle Devonian carbonates with minor shales and evaporites (Betcher et al., 1995, McCabe, 1971, Grasby and Betcher, 2002). The carbonate units crop out in the Manitoba lowlands, along a NW–SE trending zone that lies to the east and north of the Manitoba Escarpment, which marks the transition to overlying argillaceous

Data set

The climate data used in this study are from the historical Canadian climate database (version 2) of air temperature and accumulative precipitation (Vincent, 2001, Mekis, 2000). The temperature data are monthly means of daily maximum and minimum temperatures observed in major meteorological stations in Winnipeg and adjacent areas. The annual and seasonal means are calculated from monthly maximum and minimum temperatures. The precipitation data are monthly and annual accumulative sums of

Temperature is an important factor in groundwater level fluctuations

The above analysis demonstrates that, in general, precipitation and temperature both have a strong correlation with groundwater levels in the carbonate rock aquifer. In areas where the confining layer (Wisconsianan sediments) above the aquifer has been artificially removed or thinned, unique trends are observed. For example, east of Winnipeg, where construction of the Red River Floodway has exposed the aquifer to the surface or near surface, hydrographs in the area (e.g. G05OJ014, Fig. 8) show

Conclusions

Data analysis reveals that periodicity in climate variables is common. The longest recognizable cycle in precipitation and temperature from the Winnipeg data set is about 60 years. Sixty-year climate cycles are also observed in other regions in Canada, where it is attributed to the PDO. However, the causes of the 60-year climate cycle observed in this region and its relation with similar cycles observed elsewhere need more rigorous investigation.

Annual precipitation and annual mean temperature

Acknowledgements

Bob Betcher and Frank Render of the Manitoba Water Branch provided support for this study. Manitoba Water Resources Branch provided historical monitoring well records used herein. Canada Climate Adaptation Fund through Prairie Adaptation Research Corporation provided partial financial support for this study. We thank Rick Raddatz, Environment Canada, who provided the grass and wheat soil moisture data in the Winnipeg area. The authors are grateful to Dr Dale Issler of Geological Survey of

References (39)

  • R.A. Freeze et al.

    Groundwater

    (1979)
  • T.Y. Gan

    Hydroclimatic trends and possible climatic warming in the Canadian prairies

    Water Resources Research

    (1998)
  • Gehrels, J.C., 1999. Groundwater level fluctuations. Separation of natural from anthropogenic influences and...
  • S. Grasby et al.

    Regional hydrogeochemistry of the carbonate rock aquifer, southern Manitoba

    Canadian Journal of Earth Sciences

    (2002)
  • N. Hafmann et al.

    Climate change and variability: impacts on Canadian water

    (2000)
  • G.M. Hornberger et al.

    Elements of physical hydrology

    (1997)
  • J.E. Lewis

    Climatic change and its effects on water resources for Canada: a review

    Canadian Water Resources Journal

    (1989)
  • M. Lissey

    Interbasinal groundwater flow, Oak River, Manitoba

    (1966)
  • H. Maathuis et al.

    Potential Impact of Climate Change on Prairie Groundwater Supplies: Review of Current Knowledge

    (April 2000)
  • Cited by (0)

    View full text