Guelph Water Management Group

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1 Page 1 of 10 Guelph Water Management Group Home > Watershed Characterization Project > Annapolis Valley Water resources and extreme events Annapolis Valley Surface waters The Annapolis Valley is approximately 100 km long, running between the Annapolis and Minas basins [1]. The six primary subwatersheds in the Annapolis Valley include the Annapolis, Canard, Cornwallis, Habitant, Gaspereau, and Pereaux subwatersheds. The size and average discharges of each of these rivers vary significantly. The Pereaux River is the shortest, with a main stem less than 4 km long; the Annapolis River s main trunk is the longest at 150 km [2, 3]. The Pereaux River drains a watershed that is under 9 km² [4], while the Annapolis River drains over 2000 km² [5]. Between January 1984 and December 1994, the Pereaux River had a minimum recorded flow of cubic meters per second (cms) and a maximum of 0.9 cms; the Annapolis River had a minimum recorded flow of 2.6 cms and a maximum flow of 98.5 cms at the Village of Lawrencetown [4] (Table 3). This variability of supply challenges the balancing of human and ecological water needs throughout the seasons. There have been a number of structural changes made to the waterways in the Annapolis Valley. Dykes have been used since Europeans began to settle in the Annapolis region in the early 17th century. These rock and earth barriers were built along the rivers and the basins to reclaim salt marshes, and other land that is subject to the flooding and ebbing of the tides, for agricultural, residential and industrial uses [6]. A causeway built across the Annapolis River Annapolis Valley Report: Introduction Natural environment Climate and climate change Water resources and extreme events Water availability Physiography Human environment Institutional arrangements Watershed issues Watershed stakeholders References Map Compare the Annapolis Valley with: Maitland Valley Oldman River Grand River Big Creek

2 Page 2 of 10 in , close to the Town of Annapolis Royal, has had a significant impact on the lower reaches of the Annapolis River. The causeway replaced a bridge that had previously been located between the Town of Annapolis Royal and the Village of Granville Ferry, and fulfilled the dual purposes of meeting the needs of the expanding transportation network, and of protecting the roughly 1,740 ha of dyked farmland upriver of the causeway [7, 8]. Work to transform the causeway into a tidal station was completed in The station utilizes the power of the tides to generate enough electricity to power 4,000 homes [9]. Hydro power plants have operated in the Gaspereau and Annapolis subwatersheds for over 75 years. Water for the reservoirs needed to operate the hydro plants is stored during the winter and spring and used during the summer and fall. In the Gasperau subwatershed, the water held within the storage lakes is used for power production, fish habitat and passage, and recreational use. While the system does not have the capacity to run through the driest part of the summers, any water that is stored during this time is used to maintain minimum flows for fish in the watershed. In the Annapolis subwatershed, on the Nictaux River, the generating station runs at full capacity from November to June. However, in the summer and early fall, electricity production is limited by a lack of water and a need to maintain minimum water levels for fish and fish habitat. On the South Annapolis River, also in the Annapolis subwatershed, flows are lowest from July to September, and the Berwick Electric Commission is required to maintain, to the best of their abilities, a flow of at least 6,750 litres per minute [4]. Reservoirs play a key role in ensuring an adequate supply of surface water for power production, ecosystem health, and recreation opportunities in the Annapolis Valley. Water quality Surface waters throughout the Annapolis

3 Page 3 of 10 Valley are extremely susceptible to contamination from land use activities. Pollution in the river is suspected to originate from a variety of sources including public sewage treatment plants, runoff of from farmlands, and poorly constructed septic systems in residential areas [12]. Phosphorus concentrations in Kings County lakes have risen since 1997; nitrogen concentrations have increased since 1989, in both streams and lakes; the Cornwallis River has fecal coliform levels reported to be above acceptable levels for drinking, recreational, and agricultural uses; and many shellfish beds in the region have been closed [10]. The Cornwallis River was in fact listed as one of Canada s top ten most endangered rivers in 2002, due in part to the high levels of fecal contaminants in the water [11]. The Habitant, Pereaux, and Canard rivers are also plagued by problems associated with the leaching of agricultural fertilizers, with excess phosphorus and nitrogen being recorded in all three rivers [13]. The Habitant and Canard rivers experience high water temperatures, lowering their suitability for cold-water fish habitat. The Annapolis River suffers from many of the same ailments as other rivers in the Valley, with animal manure washing into the river during rain events, inadequate public and private sewage systems polluting the water, and land clearing for farming and forestry operations increasing sediment loads in the river [14, 15]. One pervasive problem in the Valley, is the fact that cattle have unlimited access to waterways [16, 17]. The problem with cattle in the rivers, is that they trample stream banks, increasing sedimentation; remove riparian vegetation, increasing stream temperatures, and destabilizing stream banks; and their feces are deposited directly in river waters which increases fecal coliform levels in the water [18]. A study of the Pereaux, Habitant, and Canard rivers reported that fecal coliform counts, which indicate fecal contamination from warm-blooded animals, taken from each

4 Page 4 of 10 of the rivers, were above 100 / 100ml in more than half the water samples taken between May 16 and August 28, 2001 [13]. A fecal coliform count of 100 / 100ml is the maximum allowable level in water used for irrigation of crops for human consumption [13]. Groundwater Groundwater is the largest source of fresh water in the Annapolis Valley. Triassic Wolfville sandstones and conglomerates make up the bedrock that underlies the lowlands of the Valley, providing a stable supply of water throughout the region. Wells drawing from the Wolfville aquifer commonly yield several hundred imperial gallons of water per minute. Localized deposits of glacial sand and gravel, found mainly in the eastern and central portions of the Valley, are important sources of groundwater with potential well yields of over a thousand imperial gallons of water per minute [1]. The most comprehensive survey of the groundwater resources in the Annapolis Valley to date outlines several groupings of bedrock material that influence the quantity and quality of groundwater in the Valley [1]: Slates and quartzites: Composed of early Palaezoic rocks from the Goldenville Formation and the Torbrook Formation. These formations are composed of metamorphic rock that yields water in areas where the rock is fractured. These formations are found along the South Mountain highland and provide an economical source of water for domestic use with average yields of 3 to 4 imperial gallons per minute (igpm). Water in this unit is low in hardness and dissolved solids, but can be more acidic than the North Mountain basalts. Therefore, they can contain high levels of iron and manganese. Granite: Composed of granites, this formation makes up a large portion of the South Mountains. Yields from

5 Page 5 of 10 granite, which often contains joints that are nearly parallel to the surface slope, can be haphazard, with wells a hundred meters apart yielding radically different amounts of water. Average yields of 9 igpm have been recorded, but yields of 3 to 4 igpm are all that should be expected. Water in this unit can contain more calcium bicarbonate than water found in metamorphic rocks or basalt. Horton Group: Composed of a number of different types of rock such as shale, siltstone, sandstone, grit, and conglomerate, this group is found underlying the Gaspereau subwatershed. The aquifer is under artesian pressure, and wells can be expected to produce between 10 and 100 igpm. Water quality in this formation can be affected by proximity to estuaries, which increases the potential for high chloride levels. Water in this area also tends to have higher levels of dissolved solids and is harder than water from upland units. Wolfville Formation: Composed of sandstones and conglomerates with imbedded siltstones and claystones, this formation underlies most of the lowlands of the Annapolis Valley. Yields from this formation vary throughout the Valley depending on saturated thickness, and the specific composition of the region of the aquifer being penetrated by a well. Most of the water in this formation moves through intergranular pore space and to a lesser extent through joints. Wells that tap into this formation can be expected to produce between 100 and 500 igpm. Water quality from this formation is generally good but contains more dissolved solids, including ions of calcium and calcium bicarbonate, than water from the upland units. Water from this formation tends to have higher alkalinity, hardness, and ph, than the water from surficial sands and gravels. Well water from low-lying areas near estuaries at the ends of the Valley can

6 Page 6 of 10 be affected by sodium chloride. Water from high production wells at the ends of the Valley is particularly vulnerable to saltwater contamination. Blomidon Formation: Composed of finegrained rocks such as siltstone and claystone, this formation only yields small quantities of water. The formation is located along the North Mountain scarp, where occasional pockets of sandstone can be found. Water from this formation often escapes to the surface along the face of the North Mountain as springs, and is used to a limited extent for irrigation, but more commonly for domestic use due to the low water yields. Calcium sulfate and calcium bicarbonate are among the most important dissolved constituents in this formation, causing it to contain higher dissolved solids and be harder than other units in the Valley. Water from the springs tends to contain fewer dissolved solids than water from wells drawing from this formation. North Mountain Basalt: Composed of lava flows, North Mountain Basalt has water in joints and the upper vesicular portion of basalt flows. Water flow within the basalt is limited and yields range from less than 1 to 40 igpm. It is suspected that water filters downward through the North Mountain Basalt and into the Blomidon Formation. Water in this unit is of excellent quality with low dissolved solids, hardness, and iron. Sand and gravel aquifers, as mentioned above, can be found in the Valley and offer some potential as water supplies, especially where deposits are greater than 10 meters in depth. In these situations, yields of 100 to 1,000 ipgm can be expected. However, where saturated sand and gravel is limited in depth, bedrock aquifers offer the best opportunities for developing reliable water supplies [1]. Water quality

7 Page 7 of 10 Groundwater contamination is a key issue in the Annapolis Valley, especially with many communities in the Annapolis Valley turning from surface water supplies to groundwater supplies (e.g., Town of Kentville, Town of Middleton, Town of Wolfville). One particularly troubling type of pollution is long range transportation of acidifying emissions and heavy metals, such as mercury, from industrialized areas of the United States and central Canada [19]. In Kings County, research into rural well water supplies shows that contamination from pest control products is not problematic in rural wells, but low levels of pesticides, particularly atrazine, are still being recorded. Contamination of wells by nitrate-n and bacteria is a concern, with levels of both contaminants exceeding standards set in Health Canada s Guidelines for Canadian Drinking Water Quality in some wells in the Valley. In Canning, 29 percent of the rural wells sampled exceeded acceptable levels for nitrate-n [20]. High nitrate levels are a concern because it causes blue baby syndrome in infants less than four months old [21]. Local reliance on groundwater for drinking water supplies, combined with the vulnerability of groundwater resources to contamination from past, current, and future land uses, makes the protection of groundwater quality a key water management issue in the Valley. Extreme hydrological events Flooding Flooding does not happen very frequently in the Annapolis Valley. The floods that do occur are most likely to take place during the spring melt, when the melt water is combined with onshore winds and seasonal high tides (about a 20 year cycle) [22]. In the Town of Wolfville, there have been two historically significant floods, one in April 1977 and the other in April of The 1977 flood occurred when strong northeasterly winds, a 30 foot tide, a heavy rainstorm, and spring snowmelt all combined to flood the low areas of the Gaspereau Extension, displacing people from their houses

8 Page 8 of 10 and causing salt damage to buildings [22]. In March 2003, flooding in Annapolis and Kings counties resulted in school closures and home evacuations; other Nova Scotia communities declared states of emergency. Flooding can also take place during fall storms, although it is less likely. Heavy fall rains flooded basements and farmers fields and caused some portions of the Annapolis and Cornwallis rivers to overrun their banks in November, 2002 [23]. Flooding can also happen when storms and high tides combine to breach the dykes that protect much of Annapolis Valley s lowland farmland. In 1705 and again in 1869, storms broke through the dykes at Grand Pre, flooding the land with seawater and rendering them useless for agricultural purposes for the next few years [24]. In April of 1977, a combination of southerly winds pushing up the Bay of Fundy, low barometric pressure reducing the downward force on the water, a full moon, and the moon at a point in its orbit where it was near the earth, all combined to flood the dykes by the Village of Port Williams and the Town of Wolfville [24]. Despite the relatively low occurrence of flooding in the Annapolis Valley, flooding could be a problem in the future. Climate change scenarios for Atlantic Canada indicate that the frequency and severity of storms could increase and sea levels could rise, which will amplify the potential for floods in the region [25, 26]. Drought Drought plagued Nova Scotia in 4 of the 6 years between 1996 and 2002 [27]. Lack of annual precipitation is not generally a problem in the Valley. Normally high spring and fall precipitation levels have prompted the installation of drainage tiles below farm fields throughout the Annapolis Valley. Rather, it is a shortage of water during the summer that has farmers in the Annapolis Valley concerned [28, 29]. However, in 1999, a winter with low snow accumulations was followed by a dry spring in which Nova Scotia, on average, received 44

9 Page 9 of 10 percent of the 30-year average rainfall levels over the period of April 1 to June 30 [30]. In July and August of 2001, only 24 percent of the forty-year average rainfall for those months was reported at the Kentville climate station [2]; in May and June of 2002, Kings County only received 80 percent of the rainfall expected for that time of the year [31]. With deficits in water supplies occurring more frequently now than they have past [4], a key concern in the Valley is that the frequency or severity of droughts could increase in the future as a result of climate change. 1. Trescott, Brylinsky and Pindham, Moore, AGRA Earth and Environmental Limited, Hebert, Gorham and Daborn, Daborn and Daborn, 1991a 8. Daborn and Daborn, 1991b 9. Nova Scotia Power, Kings Community Economic Agency, Earthwild International, Nelson, Brylinsky and Pindham, Daborn and Daborn, 1991c 15. Clean Annapolis River Project, Environment Canada, Environment Canada, Natural Resources Defense Council, Atlantic Planners Institute, 2000

10 Page 10 of Nova Scotia Department of the Environment, Nova Scotia Department of Agriculture and Marketing, and Nova Scotia Department of Health and Fitness, Blair, Town of Wolfville, Simpson, Blomidon Naturalists Society, Environment Canada, Government of Canada, Delaney, Scott, Nova Scotia House of Assembly, Agriculture and Agri-Food Canada, Agriculture and Fisheries, 2002 Annapolis Valley Characterisation Report. Author: Darren Timmer, Guelph Water Management Group, University of Guelph. Last Updated: March 7, Guelph Water Management Group Department of Geography University of Guelph Guelph, Ontario, Canada N1G 2W1 Contact Us