Understanding the Potential Impacts of Surface and …potential impacts of surface and ground water withdrawal on stream biota under present and predicted abstraction scenarios. To

Fisheries Report Series

New Brunswick Cooperative Fish and Wildlife Research Unit Report #03-08

Understanding the Potential Impacts of Water Abstractions on Stream Ecosystems

of Prince Edward Island:

Final Report on the Abstraction Experiments of 2006 and 2007

Prepared for:

Canada - PEI Water Program

October 1, 2008

Prepared by:

R.A. Curry and M. Gautreau

Water Withdrawal in PEI Streams Page 1

CRI / NBCFWRU Report #03-08

EXECUTIVE SUMMARY 1. Stream water levels, temperature, chemistry, and brook trout movements

have been monitored in North Brook, Dunk River, PEI from autumn 2004 to autumn 2007.

2. The North Brook catchment is ~1,200 ha with ~5km of mainstem flowing water at the surface. Landuse is principally potato production 82%, 9% forested, and 9% in other uses (2005 data).

3. Three sites were studied in detail; these were located at stream km 0.15 (lower), 2 (middle), and 2.8 (upper). Sites were 75m in length and 4m wide (surface areas of 300m2) with average depths of 30cm.

4. At each site, continuous recording depth, temperature, turbidity probes were installed, and an array of three continuous recording PIT tag antennas separated by 25m. Just over 350 brook trout were implanted with PIT tags during the study.

5. Brook trout habitats, areas and volumes, were modeled using PHABSIM at the lower and middle sites.

6. Experimental water abstraction experiments were conducted at the middle and lower sites in 2006 and 2007 (middle site only). The experiments used pumps to remove surface water at rates used by local farmers, ~400 gal/min (2006), and then increased to a maximum of 1,600 gal/min for the 2007 experiment at the middle site.

7. The pumping experiments removed water continuously for 20-29 hrs at a site. The maximum pumping rates were estimated to be 400 gal/min (1,514 l/min) in 2006 and 1,000 gal/min (3,785 l/min) in 2007. The rate of water removal ranged from 0.55 to 6.75 cm/hr (1.06 to 16.54 m3/hr) which resulted in maximum stream level reductions ranging from 1.04 to 2.32 cm.

8. Estimated loss of brook trout habitat at these rates of surface water abstraction ranged from 2-20%.

9. Brook trout did not move into or from study reaches during the pumping experiments. We don’t know if this is related to the stream level changes or the normal behaviour.

10. PEI EEF minimum flows for the lower North Brook site allow for ~10cm of surface water drawdown compared to ~2 cm suggested by fish ecologists. It is not clear if 10cm will impact the ecosystem, but a 10cm reduction was predicted to reduce brook trout habitat by 8-34% (area).

11. Given that the brook trout population persists and the benthic community is not different in North Brook, it does suggest that the potential impact of the existing surface water abstraction regime (<2 weeks, 1-2 sites, and not in every year) is not detectable.



INTRODUCTION Surface water and groundwater are critical hydrological resources for Prince Edward Island. Surface water is required for irrigation; groundwater provides the drinking water and some irrigation resources for the island. The same freshwaters also support a rich diversity of life in island streams that includes fishes, insects, and plants, as well as other animals such as bats and birds that can depend on the food resources generated by these freshwaters. This diversity is our best measure of the health of all stream environments. Modification of a river’s flow regime can have detrimental effects on aquatic biota (Richter et al. 1997, Pringle et al. 2000). Modified flows and in particular surface water reductions negatively impact biodiversity and productivity, and change instream habitats though alterations of stream geomorphology that can reduce connectivity between habitats, the hydrological regime to which biota have adapted, and water temperature and quality (Petts 1989). For example, harmful blooms of blue-green algae in the Darling River, Australia have been linked to agricultural impoundments where reduced stream flows promoted intrusion of saline groundwater, decreasing turbidity through coagulation and settling of suspended organic matter, and ultimately resulting in increased light penetration providing optimal bloom conditions (Grace et al. 1994). Similarly, during the intensification of agricultural irrigation in the lower River Murray, Australia over the past three to four decades, riverine flora and fauna have been exposed to various flow-related modifications such as altered water levels, increased turbidity and salinity, and introduced species, all of which have led to decreased ranges and abundances of native species (Walker and Thoms 1993). Alterations of flow regimes also affect food-web dynamics by introducing stress for native populations and creating opportunities for invasions by exotic species (Power et al. 1996). Numerous studies have demonstrated that reductions in flow of streams can have significant, negative impacts on stream biota as reviewed by Skinner and Curry (2005) and Acreman et al. (2008). The effects can be acute resulting from direct loss of physical habitat and dispersal by animals, e.g., fishes and benthic macroinvertebrates, or effects can be more subtle such as alteration of habitats, e.g., fragmentation or warming during critical summer periods. The change in flow can result from the direct removal of surface water, but it also occurs when groundwater-pumping regimes lower the local water table or alter the rate of groundwater discharge to surface waters causing changes in discharge regimes. PEI has a unique geology and hydrogeology. The island is almost completely composed of sandstone bedrock that is an excellent medium for the development of extensive groundwater resources. As a result, most surface waters have stable base flows and temperatures (the groundwater influence),



and generally a greater occurrence of fine sediments and high turbidity (erosion of sandstone) than occurs across the broader Maritime region. PEI biota are locally adapted to these aquatic conditions, and therefore PEI biota generally stretch known tolerances and tactics within a species (e.g., Curry and MacNeill 2004). In recent years with expansions of potato production, there has been an increase in sediment deposition and nitrate loading in rivers and streams, as well as an increase in demand for ground and surface water for irrigation. Added to these pressures are the increasing demand for water resources by municipalities, industry, and expanding tourism operations, and all of these within the context of ongoing climate change and its potential impacts on quantity and quality of water resources. The relevance of these potential effects on stream ecosystems is unknown for PEI, across Canada, and around the world (e.g., Acreman et al. 2008). Nonetheless, water resources managers require an ability to forecast the potential impacts of surface and ground water withdrawal on stream biota under present and predicted abstraction scenarios. To be successful, managers first require a basic understanding of how biota respond to the natural hydrological regimes of PEI streams and subsequently, managers require models to predict probabilities of altered biotic responses when water abstraction alters natural hydrological regimes. Beginning in the autumn of 2004 and continuing until autumn 2007, we began a study of streams across PEI to examine the effects of water abstraction and sediment of stream ecosystem health. Our first objective was to examine the response of the dominate fish species in PEI streams, brook trout (Salvelinus fontinalis), to fluctuating stream flows and specifically during surface water abstraction periods (see annual reports listed below). We sought to observe movements and search for possible relationships with abstraction events and generally, changes in stream flow throughout the year. We measured habitat for brook trout and modelled changes during changing flow regimes. Our methods focused on one system where we tagged and monitored fish movements, recorded stream physical and chemical conditions, measured and modelled habitat changing during flow alterations, and conducted surface water abstraction experiments to monitor fish responses. Herein we report on the abstraction experiments 2006 and 2007. METHODS Study Area North Brook is a tributary to the Dunk River (Figure 1). It is about ~5km of mainstem flowing water at the surface with a catchment ~1200 ha. Landuse is principally potato production 82%, 9% forested, and 9% in other uses (2005 data). Three sites were studied in detail (Figure 1); these were located at



stream km 0.15 (lower), 2 (middle), and 2.8 (upper; Lower - 46 20' 51.8", 63 37' 53.9", Middle - 46 21' 33.7", 63 36' 52.8", and Upper - 46 21' 53.2", 63 36' 46.1", respectively). Fish Movements Movements of individual brook trout were monitored using Passive Integrated Transponders (PIT) tags and reading stations located each of three sites (Figure 1). Each station consisted of a reader, data logging unit, tuning boxes, power sources and an array of three antennas installed across the stream (3 antennas, ~25 m separation for a total area of 50m). Each antenna loop was made of five stranded 12 gauge wire looped twice, attached to a vertical frame constructed of 1.5” Pyrex tubing attached to rebar secured in the streambed (Figure 2). The reader, data logger, and power source were placed in plastic totes for protection from the weather (Cooper et al. 2007, Curry et al. 2005, 2006). Brook trout were collected at each of the three sites by backpack electrofishing. At each site, fish >12 cm were held in coolers with aerators in preparation for implantation of PIT tags. Surgical procedures followed those described by Curry et al. (2002). In general, anesthetised (0.4 ml of clove oil dissolved in 4 ml of ETOH for 10 L of water) individuals were held ventral side up by the surgeon and a small incision, ~4mm, was made into the body cavity, slightly off center and in front of the pelvic fins using a scalpel. A sterilized PIT tag (Texas Instrument 23mm tag) was inserted into the body cavity and massaged forward away from the incision. If the incision was large, a suture was applied. The fish was then placed in a recovery tank with aerators.



Figure 1. Location of North Brook in the Dunk River watershed and the PIT tag reading and water level/quality monitoring stations (red stars).

NorthBrook

Dunk RiverScale’s Pond

Station 1lower

Station 3upper

Station 2middle113

8

Freetown

109

1 km

0North Brook

Dunk River WatershedNorth Brook

Dunk River Watershed

NorthBrook

Dunk RiverScale’s Pond

Station 1lower

Station 3upper

Station 2middle113

8

Freetown

109

1 km

0North Brook

Dunk River WatershedNorth Brook

Dunk River Watershed

Middle Reach

Upper Reach

Lower Reach

Scale’s PondScale’s Pond

Dunk RiverDunk River

North BrookNorth Brook1 km1 km

North BrookDunk River Watershed

North BrookDunk River Watershed

N



Figure 2. PIT tag antenna at the Upper Site and a schematic diagram of reading stations at three sites in North Brook, PEI.



After all fish were tagged and fully recovered (swimming upright and no longer sluggish), they were released at the sites they were captured. Overall, 351 brook trout were PIT tagged and monitored for >1 day (146, 2005; 105, 2006; 100, 2007). Their average size was 16.4 + 3.3 cm FL and 59.5 + 43.9 g wet weight. Water Level and Temperature At each of the three study areas, YSI data sondes measuring temperature and water depth were deployed at the downstream limit of the three antennas of the PIT tag readers. Data sondes were operational year-round recoding every 60 min. except during the abstraction experiments when sampling was increased to every 5 min. Assessing Habitat Volumes - PHABSIM To assess changes in stream habitat, we employed the PHABSIM techniques (Figure 3 - Curry et al. 2006). At the middle and lower sites, we surveyed the 50m of area within the PIT tag antennas measuring location and depths. To determine brook trout habitat therein, we use the habitat suitability indices (HSI) for brook trout in Newfoundland streams (K. Clarke, DFO St. John’s, unpublished data). Areas and volumes for given depths were calculated for each site (Table 1). The average depth and volume relationships were used to determine volume changes during the abstraction experiments.



Table 1. Results of the PHABSIM modeling of brook trout habitat in North Brook (Curry et al. 2006).

Discharge

Average depth

Average velocity

Wetted Area Volume

Site (m3/s) (m) (m/s) (m2) (m3) 0.0 Lower 0.11 0.14 77.6 9.2

0.1 0.13 0.18 92.6 12.7 0.1 0.14 0.22 100.6 15.4 0.1 0.15 0.25 108.2 18.0 0.2 0.19 0.32 133.9 27.8 0.3 0.24 0.35 147.7 36.8 0.4 0.28 0.38 158.7 45.1 0.5 0.31 0.40 165.8 52.7 0.6 0.34 0.42 171.7 59.7 0.7 0.35 0.42 178.8 66.3 0.8 0.38 0.45 183.5 72.3 0.9 0.40 0.47 185.0 77.7 1.0 0.42 0.49 188.4 83.0 1.3 0.47 0.54 194.3 94.9 1.5 0.52 0.58 200.5 106.1 1.8 0.56 0.63 203.9 116.6 2.0 0.60 0.66 207.4 126.6 2.5 0.66 0.71 225.3 146.0

0.1 Middle 0.29 0.08 239.9 72.0 0.1 0.31 0.11 247.4 77.1 0.1 0.31 0.13 255.5 81.1 0.2 0.34 0.21 267.7 92.3 0.3 0.36 0.27 274.0 100.9 0.4 0.38 0.31 278.8 108.7 0.5 0.40 0.35 283.4 116.1 0.6 0.42 0.38 287.1 123.0 0.7 0.44 0.41 290.9 129.6 0.8 0.46 0.44 293.4 135.8 0.9 0.47 0.47 294.8 141.7 1.0 0.49 0.49 296.9 147.2 1.1 0.50 0.52 299.4 152.6 1.5 0.55 0.59 307.3 173.0



Figure 3. PHABSIM predicted changes in potential brook trout habitat for +10 cm change in water level at the Lower and Middle sites of North Brook (Curry et al. 2006).



Abstraction Experiments

The abstraction experiments were used to simulate irrigation practices used by agricultural operators. A suction pump (Figure 4) was deployed to withdraw the water. The pump extracted water from ~5m upstream of the PIT tag study site (50m in length) and discharged ~50m downstream of the site. To mitigate erosion at the discharge location, discharging water was directed into constructed channels lined with patio stones, plastic, and boulders. We monitored this area closely to ensure that pumping activities didn’t alter sediment input and disturbance in the stream. All pumped water was thus returned to the brook.

In 2006, experiments were conducted at the lower (7-8 August, 29 hrs) and middle sites (2-3 August, 20 hrs - report 2006). Our permit was granted in accordance to normal agriculture practices for abstraction at a rate of 400 gal/min; we estimated our maximum rate of pumping to be 600 gal/min and on average the rate was estimated to be 400 gal/min because of the length of hose used (Homelite FP25V, www.riversidepumpmfg.com). Pumping was continuous during the experiments, but the rate varies because of fluctuations in engine performance (rpm flux) and brief stops for refueling (<5 min; see Figures 5 and 6 to see the fluctuations in water level reflecting the pumping efficiency). In 2007, we only pumped at the middle site (result of pump availability) and the pumping rate was increased to a maximum 1600 gal/min (Gorman-Rupp 10 Series Pump, Model 16C2).

Figure 4. Pumping experiment in 2007. The pump (top) and discharging water downstream of the study site (lower).



Pumping was continuous (with normal engine fluctuations) for 26 hrs and estimated to be 1000 gal/min.

For each experiment, our YSI data sondes (+2 cm) were deployed at the downstream limit of the PIT tag study area and we deployed additional pressure transducers with greater accuracy of measure (0.3%), AquiStar® PT2X (Instrumentation Northwest, Inc.) upstream of the pump intake (5m) and at the downstream limit of the site. We report results as depth of water change (cm) from a fixed depth for the YSI data sonde (existing) and a fixed PSI recording of the AquiStar® PT2X from the onset of the experiment. In addition, we used a fixed metre stick to track changes during pumping (~2 hr intervals). These observations were highly correlated with the electronic instruments and thus confirming their accuracy. The data sonde information is reported in the figures to show the overall trends in the summer at the time of the experiments. The PT2X was used in all calculations.

We also calculated the rate of water level draw-down and return response by examining each period when a pump fluctuated in performance, e.g., each time a pump started (pumping response) and stopped (natural return rate). This method provided 2-8 events for calculations in each experiment. The water depths measured at the fixed points at each site (location of the YSI probe) were transformed into volumes of brook trout habitat from the PHABSIM analyses:

Volume of habitat (m3) LOWER = 245.06 * Water depth (cm) - 20.18

(r2>0.99) Volume of habitat (m3) MIDDLE = 380.96 * Water depth (>29cm) – 38.22

(r2>0.99) Volume of habitat (m3) MIDDLE = 192.06 * Water depth (<29cm) – 11.05

(r2>0.99)



Table 2. Summary of response to pumping in 2006 and 2007. The stream length is 50m at each site, habitat is for brook trout (PHABSIM)

Site Year

Stream length

(m)

Ave. depth (m)

Ave. width (m)

Surface area (m)

Total water

volume (m3)

Initial volume

of habitat

(m3)

Pump rate

(l/min)

Max. draw down (cm)

Max. loss of habitat

(m3)

Max. loss of habitat

(%) Lower 2006 50.0 0.36 4.0 300.0 107.33 20.4 1514 -1.63 -4.00 19.84 Middle 2006 50.0 0.51 3.9 292.5 149.71 59.3 1514 -2.32 -4.47 7.83 Middle 2007 50.0 0.54 3.9 292.5 159.22 66.0 4542 -1.04 -2.00 1.83

Table 3. Rate of change in depth (cm/hr) and volume (m3/hr) of habitat during

the abstraction experiments, showing response when pumping is initiated (pumping) and natural recovery of the stream when the pumping stopped (not pumping) for 2006 (max. 600 gal/min) and 2007 (max. 1600 gal/min).

Pumping Year / Site

Not pumping cm / hr m3 / hr cm / hr m3 / hr

2006 Lower (max. 600 gal/min) Average -3.65 -8.93 9.16 22.44 1 STD 2.10 5.15 8.09 19.81 Minimum -6.75 -16.54 1.69 4.14 Maximum -1.04 -2.55 26.72 65.47 N 8 8 8 8 2006 Middle (max. 600 gal/min) Average -1.60 -3.09 1.50 2.89 1 STD 0.69 1.33 1.03 2.11 Minimum -2.25 -4.33 0.00 0.00 Maximum -0.65 -1.26 2.34 4.71 N 4 4 4 4 2007 Middle (max. 1600 gal/min) Average -0.23 -0.54 0.48 2.52 1 STD 0.28 0.45 0.34 2.90 Minimum -0.55 -1.06 0.24 0.47 Maximum -0.05 -0.21 0.72 4.58 N 3 3 2 2



-2.5

-2

-1.5

-1

-0.5

0

0.5

1

08/02

/2006

6:00

08/02

/2006

10:48

08/02

/2006

15:36

08/02

/2006

20:24

08/03

/2006

1:12

08/03

/2006

6:00

08/03

/2006

10:48

delta

cm

up cm down cm

Middle Site2006

-10

-8

-6

-4

-2

0

2

4

6

8

10

July

27, 2

006

July

29, 2

006

July

31, 2

006

Augus

t 2, 2

006

Augus

t 4, 2

006

delta

cm

8

8.5

9

9.5

10

10.5

11

11.5

12

12.5

13

oC

brook cm up cm down cm temp temp up temp dwn

Middle Site2006

Figure 5. 2006 Abstraction Experiment: A) Changes in water level and temperature in the period before and after the experiment. B) Details for experimental period (shaded area is the experimental period). Parameters represented are: brook cm - change in stream depth; temp – stream temperature; cm down and upstr , down and upstr temp - change in stream depth and temperature at the downstream limit and 5m upstream of the experimental area.



-4

-2

0

2

4

6

8

10

Augus

t 4, 2

006

Augus

t 5, 2

006

Augus

t 6, 2

006

Augus

t 7, 2

006

Augus

t 8, 2

006

Augus

t 9, 2

006

Augus

t 10,

2006

delta

cm

8

9

10

11

12

13

14

oC

brook cm up cm down cm temp up temp down temp

Lower Site2006

-2

-1.5

-1

-0.5

0

0.5

08/07

/2006

9:36

08/07

/2006

14:24

08/07

/2006

19:12

08/08

/2006

0:00

08/08

/2006

4:48

08/08

/2006

9:36

08/08

/2006

14:24

08/08

/2006

19:12

08/09

/2006

0:00

delta

cm

up cm down cm

Lower Site2006



-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

07/30

/2007

0:00

07/30

/2007

4:48

07/30

/2007

9:36

07/30

/2007

14:24

07/30

/2007

19:12

07/31

/2007

0:00

07/31

/2007

4:48

07/31

/2007

9:36

07/31

/2007

14:24

07/31

/2007

19:12

08/01

/2007

0:00

08/01

/2007

4:48

08/01

/2007

9:36

Del

ta c

m

cm down cm upstr

Middle Site2007

-6

-4

-2

0

2

4

6

July

19, 2

007

July

21, 2

007

July

23, 2

007

July

25, 2

007

July

27, 2

007

July

29, 2

007

July

31, 2

007

Augus

t 2, 2

007

Augus

t 4, 2

007

Augus

t 6, 2

007

Augus

t 8, 2

007

Augus

t 10,

2007

Del

ta c

m

7

8

9

10

11

12

13

14

oC

brook cm cm down cm upstr temp down temp upstr temp

Middle Site2007

Figure 6. 2007 Abstraction Experiment: A) Changes in water level and temperature in the period before and after the experiment. B) Details for experimental period (shaded area is the experimental period). Parameters represented are: brook cm - change in stream depth; temp – stream temperature; cm down and upstr , down and upstr temp - change in stream depth and temperature at the downstream limit and 5m upstream of the experimental area.



RESULTS Changes in water levels

The pumping experiments removed water continuously for 20-29 hrs at a site. The final pumping rates were estimated to be 400 gal/min (15,14 l/min) in 2006 and 1,000 gal/min (37,85 l/min) in 2007 (Table 2). The stream level fluctuated during pumping (Figures 5 and 6) with a maximum reduction in the surface water level ranging from 1.04 to 2.32 cm. The draw-down was rapid and there was an apparent maximum for each site and its pumping rate, i.e., once pumping started, the water level would not decline after its initial drop during a 20-29 hour period of continuous pumping. This translated to an estimated loss of brook trout habitat ranging from 2 to 20% (Table 2). It was apparent that water levels upstream of the pumping location (~5m upstream of the study site) also responded to pumping for each experiment, i.e., water levels were highly, positively correlated with water levels at the downstream limit of the experimental area (Figures 5 and 6).

The estimated rate of water removal ranged from 0.55 to 6.75 cm/hr or 1.06 to 16.54 m3/hr (Table 3). This volume of loss from the stream, 18 to 276 l/min, was substantially less than the pumping rate. The maximum return rate for the stream when pumping was halted ranged from 0.72 to 26.72 cm/hr (4.58 to 65.47 m3/hr). Responses to both pumping and non-pumping indicate the significant volume of discharging groundwater to these sites. The three experiments (2006 Lower and Middle, 2007 Middle) provided some initial data to model potential responses of PEI streams to water abstraction (Figure 7). Because there are only three points in a 3-dimensional space, the modeled responses are fitted by eye to show the possible response surface. No equation for the surface was created. Fish Activity during Abstraction Experiments Fish were not moving during any of the water abstraction experiments. At the Lower site in 2006, one brook trout was detected twice at the middle antenna (movement within the site). At the Middle site, 4 brook trout were detected at the lower antenna only in 2006 (total of 8 detections); no brook trout were detected during the experiment in 2007. For comparison purposes, the overall rate of movement for 2005 to 2007 was 5.9 ± 39.6 m/day, and movements decreased in July and August to 3.5 ± 11.1 m/day (Cooper et al. 2007).



0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0.00 0.10 0.20 0.30 0.40 0.50 0.60

Pum

p R

ate

(l/m

in)

Average water depth (m)

5

90

70

50

30

10

Figure 7. Estimated potential loss of brook trout habitat (%) in North Brook

during water abstraction based on average water depth at three sites each 50m in length (300m2). The response surface is generated by eye. The three experimental results are indicated by black squares.



DISSCUSION The water abstraction experiments of 2006 and 2007 were designed to simulate as best as possible the real-time water removal from streams of PEI when land owners pump surface water under license for irrigating crops. The rate of pumping matched license criteria in 2006 (400 gal/min) and this was increased in the 2007 experiment (1000 gal/min).

The results indicate that it would be difficult to reduce stream surface levels >2cm along a 50m reach of stream, 300m2, while pumping and removing surface water at these rates in North Brook at least. Because of the positively correlated response 5m upstream of each site, it is probable that water level effects occur beyond the experimental reach. It is not clear how much farther upstream or downstream the results can be applied, but it is unlikely to exceed 25m (<100m total) given that the maximum drawdown at the pumping location was <3cm. It appears that surface water removal at these rates is rapidly matched by groundwater discharging to the stream, e.g., the result of an increase in hydraulic gradient caused by lowering the surface water levels (e.g., Winter 2001). Given the physical similarity of streams (hydrological regimes) in this region of PEI, our results are most probably applicable to many other streams with similar widths, depths, discharge, and rates of groundwater recharge. Normal surface water levels are the manifestation of the local water table. Deeper water such as pools have greater volumes of water and intersections with shallow groundwater flow (e.g., Winter et al. 1999), and such locations will affect the response to surface water abstraction. For example, in North Brook the Middle site is substantially deeper on average than the Lower site and consequently, the water level effects during pumping are muted at the Middle site (see Table 2). These results demonstrate the importance of knowing water depth and therefore volume for predicting changes due to surface water abstraction. On average, brook trout moved 3.5m/day and most often 0.0m/day in July and August in North Brook (Cooper et al. 2007). During the abstraction experiments, brook trout movements were negligible. There was no clear evidence that fish moved from or into experimental areas during the pumping periods. As a result, it is difficult to determine if this can be interpreted as normal (average) behaviour or if brook trout stopped moving within study reaches during the pumping period. The surface water abstraction was predicted to reduce brook trout habitat up to 20%. Habitat loss could be modeled in terms of average stream depth and pumping rate, but the model is provisional and requires more data to be properly validated. Nonetheless, it is consistent with known hydraulic properties



of streams, i.e., deeper water should reduce impacts and higher rates of pumping should increase impacts of surface water removal.

The next challenge for stream ecologists worldwide is determining the critical minimum habitat fish and other species require and knowing this will vary among seasons and life history stages (e.g., Acreman et al. 2008). The immediate question for PEI streams arising from our studies remains, “is a 20% loss of habitat in a PEI stream biologically significant?” The general opinion of fish ecologists (at present) is that 80% of the flow must remain after flow exceeds the Q95

for the reach, i.e., no abstraction if Q95 is not attained (Acreman et al. 2008). This is more conservative than the existing PEI EEF policy of a minimum flow of 70% of the long-term, mean monthly flow for July and August. For example, at the Lower North Brook site, PEI EEF minimum flows would allow for ~10cm of surface water drawdown compared to ~2 cm that is suggested by Acreman et al. (2008) based on our data for this site (2005-2007). We still don’t know if 2cm or as much as 10cm reduction is safe for protecting stream ecosystems, but we have predicted that a 10cm reduction in surface water level at the Lower site will reduced brook trout habitat (area) by 8-34% (Curry et al. 2006). Our studies of the benthic community in streams of the area indicate no differences from North Brook, however, we can’t separate out the water abstraction response from the many other potential stressors these PEI stream experience, e.g., erosion and sedimentation, agrochemicals, etc. Given that the brook trout population persists and the benthic community is not different in North Brook, we can suggest that the potential impact of the existing surface water abstraction regime (<2 weeks, 1-2 sites, and not in every year) is not detectable. REFERENCES Acreman, M., M. Dunbar, J. Hannaford, O. Mountford, P. Wood, N. Holmes, I.

Cowx, R. Noble, C. Extence, J. Aldrick, J. King, A. Black, & D. Crook. 2008. Developing environmental standards for abstractions from UK rivers to implement the EU Water Framework Directive. Hydrological Sciences 53:1105-1120.

Cooper, G., Curry, R.A., and M. Gautreau. 2007. Understanding the Potential Impacts of Water Abstractions on Stream Ecosystems of Prince Edward Island. New Cooperative Fish and Wildlife Research Unit, Fisheries Report #03-07.

Curry, R.A. and S. MacNeill. 2004. Population-level responses to sediment during early life in brook trout. J. N. Am. Benth. Soc. 23:140-150

Curry, R.A., J. Culp, D. Baird, M. Gautreau, O. Logan, and K. Heard. 2005. Understanding the Potential Impacts of Surface and Ground Water Withdrawal on Stream Ecosystems of Prince Edward Island: Summary



Report 2004. New Brunswick Cooperative Fish and Wildlife Research Unit, Fisheries Report #05-03.

Curry, R.A., J.C. Culp, D.J. Baird, M. Gautreau, and O. Logan. 2006. The Potential Impacts of Surface Water Withdrawal on Stream Ecosystems of Prince Edward Island: Phase I (2004-05). New Brunswick Cooperative Fish and Wildlife Research Unit, Fisheries Report #03-06.

Grace, M., Hart, B.T., and R. Oliver. 1994. Effects of a saline intrusion under low flow conditions in the Darling River. Proceedings of the AWWA Environmental Flows Seminar, pp. 119-124. Australian Water Resource Association. Artarmon, New South Wales.

Logan, O. 2008. Effects of fine sediment deposition on benthic invertebrate communities. M.Sc. Thesis, University of New Brunswick, Fredericton, NB.

Petts, G.A. 1989. Perspectives for ecological management of regulated rivers. In Alternatives on Regulated River Management, pp. 3-24. Edited by Gore, J.A. and Petts, G. CRC Press, Boca Raton, Florida.

Power, M.E., Dietrich, W.E., and J.C. Finaly. 1996. Dams and downstream aquatic biodiversity: potential food web consequences of hydrologic and geomorphic change. Environmental Management 20:887-895.

Pringle, C.M., Freeman, M.C., and B.J. Freeman. 2000. Regional effects of hydrologic alterations on riverine macrobiota in the New World: tropical–temperate comparisons. BioScience 50:807-823.

Richter, B.D., Baumgartner, J.V., Wigington, R. and D.P. Braun. 1997. How much water does a river need? Freshwater Biology 37:231-249.

Skinner, M.A. and R.A. Curry. 2005. Threats from Excessive Water Removal to the Maintenance of Ecological Integrity of Watersheds in Major Agricultural Regions of Canada: Literature Review and Annotated Bibliography. New Brunswick Cooperative Fish and Wildlife Research Unit, Fisheries Report #05-01.

Winter, T.C. 2001. The concept of hydrologic landscapes, Journal of the American Water Resources Association 37:335–350.

Winter, T.C., Harvey, J.W., Franke, O.L., and Alley, W.M. 1998, Ground water and surface water a single resource. U.S. Geological Survey Circular 1139.

Documents

Understanding the Potential Impacts of Surface and …potential impacts of surface and ground water withdrawal on stream biota under present and predicted abstraction scenarios. To