Rural water well infrastructure assessment on the Prairies: An Overview of Groundwater Development and Reliance Trends

In the Canadian Prairies, water well infrastructure innocuously dots the Prairie landscape. However, very little is known about the actual condition or distribution of the water well infrastructure on which much of the rural population depends. Groundwater is the preferred water supply source in most rural areas, since it is readily available and accessible over large portions of the semi-arid Prairies. It is also regarded to be a supply alternative with a marked degree of drought tolerance. The most significant consequence of climate change, with a shift to drier conditions and more frequent drought events, will likely be an increased reliance on groundwater through withdrawal wells. Such conditions can be logically assumed to stress the operation of the water well infrastructure, and therefore, this current review is a necessary step in ongoing efforts to foresee climate adaptation challenges and to develop approaches that will allow water wells to endure drought conditions without disruption at these critical times.

This report strives to provide an insight into the relationship between the nature and distribution of water well infrastructure, the patterns of groundwater development, the major geographical influences and the changing demographic patterns of groundwater reliance. This overview of the state of water well infrastructure is derived from a collaborative effort undertaken by each of the groundwater management agencies for the three Prairie provinces. The long-term provincial vision and commitment to maintaining water well data, and guiding the databases to their current state, has permitted the preparation of this material, and is gratefully acknowledged. For a detailed account of the database analysis provided by each province, the reader is referred to the reports referenced in Section 4.0 (Blechinger; Erin Consulting Ltd.; Manitoba Water Resources Branch).

Project rationale

The provincial water well databases comprise the most complete historic record of well construction and use, and therefore, were used intensively in this examination of Prairie water wells. Recent adaptation of digital data archiving, largely since 1970, and processing via GIS technology has permitted an unprecedented opportunity for comprehensive, Prairie-wide examination of water wells in a visible thematic format context with other data forms.

Water wells are reliant on a multiple of systematic factors, which together influence their productivity. The most significant factors are aquifer extent, physical storage and transmission parameters, well design characteristics and operational water levels. The infrastructure challenge addressed in this report, pertains largely to the latter two factors. Under a drought scenario, reduced levels of recharge to an aquifer can be anticipated to impact operating water levels in a well almost immediately, either because of natural groundwater level decline (involuntary adjustment) or by an increased operational drawdown created by larger withdrawal demands (voluntary adjustment).

Deep wells, considered to be greater than 15 metres in depth in the context of this report, are generally expected to be buffered from the effects of reduced recharge intervals and concerns for involuntary climate impacts are usually not regarded to be a major concern. Shallow wells, considered to be less than 15 metres in depth in the context of this report, are generally considered to be most vulnerable to drought, since these wells are most directly affected by climatic events and reduced levels of recharge. For the drought-focused purposes of this overview, it was felt to be particularly useful to examine the distribution of the shallow well component of the water well population, as this population component is at greatest risk to the impacts of drought.

Prairie Rural Water Well Infrastructure Overview

The wide distribution of water wells implies the availability of groundwater virtually everywhere in the Prairie region. However, the degree of reliance on groundwater to support development and expanding/changing rural enterprises accounts for the different population densities that are reflected by the water well distribution patterns, as shown in Figures 1 and 2.

Based on the results of the provincial analyses of their water well databases, over 390,000 water wells have reportedly been constructed since 1961 on the Prairies for groundwater withdrawal. Presently, the average replacement cost per well is estimated to be about $4000 to $5000, depending on well depth and construction materials. This investment in water wells on the Prairies, about $1.8 billion, while in itself substantial, does not consider the ancillary investments in our economy which this investment directly supports by way of water supply. As a result, even brief periods of supply disruption may impart considerable hardship and economic loss at times when these water supplies are critically required.

In all three Prairie Provinces, the average age or condition of the water well infrastructure is indeterminate, since existing databases, with the exception of Alberta, do not record wells that are now inactive or "abandoned". These databases are therefore cumulative record sets, which typically represent all wells reported at their time of construction. Most wells in the Prairies are "drilled" wells, which have been installed with the use of rotary drilling equipment. These wells are generally regarded as a small diameter wells, typically 125 to 150 millimetres (5 to 6 inches) in diameter. These drilled wells usually only partially penetrate the aquifers into which they are installed and, from an operational perspective, rely on aquifer storage to meet water supply demands. In the case of shallow wells, it is interesting to note that approximately one half of these are large diameter bored wells, typically 60 to 90 centimetres (24 to 30 inches) in diameter, which may be completed to depths significantly below their intake level. Consequently, there is a high reliance on water stored in the well casing itself, which mitigates to an extent the low production capability of some of these shallow aquifers. However, this construction practice also provides a false sense of security, since these wells are still very susceptible to drought conditions and would be the first wells impacted by reduced recharge and increased use in times of drought.