JUNCHENG HU

GROUNDWATER PREDICTIVE MODEL ON THE EFFECT OF LAND USE IMPACTS ON THE HOPINGTON AQUIFER IN LANGLEY,

BC

Groundwater Predictive Model on the Effect of Land Use Impacts on the Hopington Aquifer in Langley, BC

Part 1: Introduction

Abstract: The Hopington AB Aquifer is one of the most vulnerable unconfined aquifers in the lower

mainland. It is reported that the Hopington AB aquifer water level is decreasing year by year. The predictive model indicates that these declines are due to excessive extraction, climate change and expected population growth will only accelerate the drop in water tables. In order to address the groundwater quantity issue, a groundwater management plan is needed to regulate and protect the unconfined aquifer.

Due to climate change, expanding population and predicted droughts, anthropogenic water

use will increase. These trends will lead to higher groundwater declining rates around the world, particularly for Mediterranean semi-arid ecosystems. For instance, about one third of the world’s major aquifers are over-used and have declining water tables (NASA, 2002). In the past 50 years, groundwater is the most extracted raw material with the withdraw rates of approximately 982 km3/year, of which about 70% of pumped groundwater is used for agriculture (Margat et al. 2013). In addition, 50% of groundwater is used for drinking water resources worldwide (Smith et al. 2016). Globally, about 38% of irrigated lands are equipped for irrigation with groundwater (Siebert et al. 2016). Excessive groundwater depletion affects major regions of North Africa, the Middle East, South and Central Asia, North China, North America, Australia and localized areas throughout the world (Konikow et al. 2009).

The temporal development of groundwater storage depends on (1) the inflow into

groundwater body from the soil or from surface water bodies (recharge) and (2) the outflow from the groundwater to surface water bodies (base flow) or due to groundwater abstractions. All groundwater extraction projects, like pumping well, initially lead to a drawdown of the unconfined aquifer water table within the cone of depression of hydraulic heads around the pumping well. If the lowered hydraulic heads have induced a decrease of base flow or an increase of groundwater recharge that balance the abstractions, the cone of depression will remain stable (Zhou, 2009). Then, groundwater storage stabilizes at a lower equilibrium level as compared to the situation without groundwater abstractions. However, if groundwater abstractions cannot be balanced by increased recharge and decreased discharge over a period of years, a long-term decline of hydraulic heads and groundwater storage occurs, i.e., GW declining will result (Doell etal.2014). In the Hopington AB area, the overuse of domestic water and irrigation water use has caused the groundwater table decrease year by year. Urbanization also impacts the lower recharge rate of precipitation due to the increase of imperious layer.

The causes and impacts of groundwater depletion are neither obvious nor easy to assess. For

example, groundwater pumped from confined aquifers may be largely derived from leakage from adjacent aquitards, but leakage of low-permeability layers is difficult to estimate, rarely monitored and usually overlooked. Likewise, the decreasing water tables make groundwater less available to phreatophytes and reduce groundwater discharge to springs, streams and wetlands (Konikow et al. 2009). Where a stream is hydraulically connected to an aquifer, streamflow may be reduced by

decreasing groundwater discharge into the stream or by inducing seepage from the stream into the aquifer (Eloise et al. 2006). Also, it is difficult to distinguish the interactions between surface water and groundwater.

Groundwater depletion is of increasing concern around the world, and it is meaningful to

develop predictive models to determine the effect of land use under different scenarios, such as climate change and population growth. Hopington AB Aquifer is one of the most vulnerable groundwater in BC, thus studying the groundwater balance problem in this area is more realistic and representative. Based on the outcome of the predictive model, recommendations are needed for local government and residents to realize sustainable use of groundwater resources.

Study Area: Hopington Aquifer, Langley, BC

The Hopington Aquifer is located in the Salmon River watershed within the Township of

Langley and part of the City of Abbotsford. During summer time, the shallow, unconfined Hopington Aquifer helps sustain baseflow in the Salmon River, which supports at least 15 species of fish, including salmonids and endangered Salish Sucker. Besides that, the Hopington aquifer provides nearly 50% of the water use in the Township of Langley. However, the aquifer water level has been declining by roughly 30 cm per year over the past decade because of the overuse of well water extraction. The overuse of groundwater is the dominant reason for the declining groundwater level (Township of Langley, 2002). These declining groundwater levels correspond to increased groundwater use in the aquifer and increase the risk of lower summer baseflows and increased ecological stress to the Salmon River.

Fig 1. Overview of the Salmon River watershed and the Hopington Aquifer (Golder Associate

Ltd. 2002)

Figure 2 Water Levels in Provincial Observation Well #7 In Langley (Golder Associate Ltd.

2002)

Part 2: Objectives and data resources

2.1 Project Objectives & Goals: The overall goal of the project is to determine the water balance of the Hopington Aquifer

and its possible impact on streamflow in the Salmon River. The aim is to develop a predictive model to determine the effect of land use activities and water use on the Hopington Aquifer, to show if the aquifer is used in a sustainable manner and to evaluate if changes affect the stream water flow in the Salmon River. This model will help calculate the water balance in the study area. The first step in the hydraulic cycle analysis is to define the system and then focus on the inputs

and outputs of the groundwater system. Once a water balance calculation is established, the model can show if the groundwater level has changed. Predictions can then be made using climate change and/or population growth scenarios. Finally, recommendations will be made to show the effects of possible impacts of future land use, ecosystem alteration, population growth and climate changes on the water balance of the aquifer and the stream discharge.

The specific objectives of the project will be:

Determine the water balance in the study area Build a predictive model on the effect of land and water use Apply a predictive model to different scenarios Make recommendations based on different scenarios to predict potential impacts of land

use, population and climate changes Provide potential solutions to mitigate the negative impact of GW decline.

The water balance model is used to assess whether the aquifer is used in a sustainable

manner. The Hopington AB is an unconfined aquifer consisting primarily of gravel and sand and is

dissected by the Salmon River, which receives significant amounts of groundwater particularly in the summer season (Naugler 2007). The aquifer helps sustain baseflow in the Salmon River which supports at least 15 species of fish, including salmonids and endangered Salish Sucker. At the same time that Hopington aquifer provides nearly 50% of the drinking and irrigation water use in the Township of Langley. However, there is evidence (Golder Associate, 2017) that the aquifer water level has been declining by roughly 30 cm per year in the past decade because of the overuse of pumping wells. The overuse of groundwater is the dominant reason for the declining groundwater level (Township of Langley, 2012). These declining groundwater levels correspond to increased groundwater use in the aquifer and increase the risk of lower summer baseflows and increased ecological stress to the Salmon River.

Information collected for the purpose of hydrology assessment included climate data

(precipitation, temperature, evapotranspiration), stream flow, and discharge data.

Part 3: Assumptions and Methodology

3.1 Assumptions

1) The inflow and outflow are assumed to be equal between the Hopington AB aquifer and other hydraulically connected aquifers.

Since the hydraulically connected aquifers have groundwater flow between them,

depending on the difference between the hydraulic heads, the rate of groundwater flows between different aquifers will change. However, due to the limitations of this model, it is not possible to calculate the groundwater flow between different aquifers. According to the underground model established by Golder Associate (2016), the results show that there is a

certain amount of outflow and inflow exchange between Hopington AB and other hydraulic connected aquifers, but the total annual variation of total inflow and outflow is roughly the same.

2）5% leakage of total water use will recharge According to GVWD's estimate in 1999, about 10% of total water will enter the

groundwater due to the leakage of underground pipelines. Therefore, in this predictive model, the leakage of underground water pipes was also taken into account. The water pipeline network is not as dense as in other areas, so a 5% recharge rate is used in the model, which is more in line with the actual situation. In addition, since there is no statistical data on total regional water use in the region, it is assumed that the total water consumption is balanced with the amount of groundwater extracted through private wells.

3) Within the urban land use, only 10 % of the precipitation will eventually recharge the

groundwater. Precipitation is the main recharge source of groundwater, but due to the different types

of land use, the amount of rainfall that can eventually enter the groundwater will vary. According to the recommendations, this model assumes that only 10% of the precipitation will eventually recharge the groundwater within the urban land use.

4) Within the agricultural and forest land use, 65% of the precipitation will eventually

recharge the groundwater. Precipitation is the main source of groundwater, but due to the different types of land

use, the amount of rainfall that can eventually enter the groundwater will vary. In these two land uses, the precipitation can effectively enter the soil and then recharge the groundwater. In my model, I assumed that 65% of the precipitation can effectively replenish groundwater within the agricultural and forest land use.

5）Rainfed and Irrigated Agriculture Artificially irrigation can lead irrigation water to recharge the groundwater, but if

irrigation is properly applied, there should be little water recharging the aquifer. At the same time, anthropogenic irrigation water is also part of the total water use. Due to the lack of data on water use for irrigation, artificial irrigation practices will be ignored in this model for groundwater replenishment. So, the model ideally assume that precipitation is the main source of water in agriculture.

3.2 Methodology In the predictive model, it was assumed that the groundwater table variations in the

Hopington Aquifer are determined by the differences in water input and output. As shown in the formula 1 below, the data are analyzed on a monthly basis.

Change =INPUT- OUTPUT 1 The input includes effective precipitation, surface water inflow to groundwater, and

pipeline leakage. As shown in Formula 2 below. INPUT= Effective Precipitation + Leakage + Surface Water Inflow 2 The precipitation was divided into two parts, based on the assumptions given above. The

effective recharge rate of the precipitation was 10% on urban land use and 65% on agricultural land use and forest land use. As shown in Formula 3.

Effective precipitation = 10% urban + 65% agricultural & forest 3 The output consists of ET, Groundwater Outflow to Surface Water and GW Outflow from

pumping. As shown in Formula 4. OUTPUT= GW pumping + ET + GW Outflow 4 The water level change of the groundwater is calculated by the above formula on a

monthly basis, and the final result is plotted as a one-year cumulative change line chart.

Part 4: Data analysis

4.1 Precipitation The Fraser-Delta region can be characterized as having warm, rainy winters and relatively

warm, dry summers (Halstead, 1986). During the winter season, in the study area, a fairly steady succession of cloudy, rainy conditions persists, however the summertime has a steady long period of sunny weather with low precipitation.

The climate data was analyzed over four seasons, representing wet and dry conditions:

(1) Spring and Winter (wet period): from October 1 to March 31 and (2) Summer and Fall (dry period) from April 1 to September 30. Nearly 80% of the total annual precipitation is generated in the Winter and Spring. As for Summer and Fall from April 1 to September 30, the weather is a fairly sunny, and dry conditions prevail with relatively low precipitation. During the wet season, when precipitation is the heaviest and temperatures are low, evapotranspiration is at a minimum. This indicates that during October to March period, most of the precipitation is available to potentially recharge the groundwater.

Precipitation data was normalized for the period of 1990-2018 in Table 1. (See in

Appendix)

The climate trends are shown in Fig 3 for the 1990 to 2018 period. The total annual precipitation has a slightly downward trend. In order to apply Scenario 1 (Climate change effect), as the straight-trendline shows, that in the next five years the annual total precipitation is projected to decrease from around 1700 mm to 1500 mm per year with fluctuation.

Fig 3. Annual total precipitation trend The seasonal precipitation trend is shown in Fig 4. for the wet and dry periods (October

1 to March 31 and April 1 to September 30). Nearly 80% of the total annual precipitation generates in the wet period.

Fig 4. Monthly Precipitation Variation According to Fig 4, the monthly total precipitation throughout the year has different

trends. Therefore, in order to analyze the changes in monthly total precipitation throughout the year, this article divides the year into four seasons to analyze the trend of total precipitation in different seasons.

Fig 5. Spring total precipitation trend (Jan to Mar)

Although the annual total precipitation is projected to decrease gradually, the total

precipitation during Spring will increase as shown in Fig 5. Based on the upward straight-trendline the changes between 1990 and 2018 show an overall increase of about 50 mm. Over the next five year it suggests that the Spring precipitation will be around 550 mm with fluctuation.

Fig 6. Summer total precipitation trend (Apr to Jun) The Summer precipitation shows a significant downward trend with a decline of about

100 mm. As summer total precipitation data shows, in the next five years, the summertime in the study area will be dryer with an average projected average of around 270 mm.

Fig 7. Fall total precipitation trend (July to Sep) Similarly, the fall precipitation (Fig 7) shows a downward precipitation trend with a

decline of about 50 mm between 1990 and 2018 with an average precipitation over the past 5 years of around 180mm.

Fig 8. Winter total precipitation trend (Oct to Dec)

The winter period also shows a decline in precipitation of around 80 mm between 1990 and 2018 with an average precipitation of the past 5 years of around 600mm (Figure 8).

To summaries the current precipitation data and projected changes in Hopington AB

aquifer, the annual total precipitation will decrease gradually with more precipitation in Springtime but less precipitation in other seasons. The projected seasonal total precipitations are presented in the Table 2 and Fig 9 below.

Fig 9. Predicted Seasonal Total Precipitation As we can see in Fig 9, in the near future, Spring and Winter seasonal precipitation

account for roughly 72% annual total precipitation whereas dry seasons (summer and fall) only contributes 28%.

4.2 Streamflow

Within the study area, Hopington AB is hydraulically connected to both Salmon River and the Nicomekl River. The monthly mean discharge data from Salmon River (Station 08MH090) was analyzed to show the trend and analyzed the interaction between surface water and groundwater.

In order to analyze the interconnections between surface water and groundwater. We

need to compare the trend between annual total precipitation and salmon river mean annual discharge rate. Consider local climate pattern, we should also analyze salmon river streamflow on seasonal basis.

As aforementioned, the Hopington AB is hydraulically connected to both Salmon River and the Nicomekl River. However, the Nicomekl River lack qualified data and the impact from the aquifer is relatively small. Thus, the project only focusses on the interactions between Hopington AB aquifer and Salmon River. And the data were obtained from Environment Canada and normalized from 1969 to 2016 in Table 3. (See in appendix)

Fig 10. Mean Annual Discharge Trend As Fig 10 shows, the mean annual discharge for Salmon River has no significant upward

or downward trend. There is no significant trend in the mean annual discharge in Salmon River from 1969 to 2016. Since the annual total precipitation has decreased year by year due to the impact of climate change, the result indicates that the surface water is being replenished from the unconfined aquifer Hopington AB in a consistent manner. The project will further investigate the interrelationship between the groundwater and surface water interactions, by examining the seasonal mean river discharge data.

Fig 11. Mean monthly discharge 1996-2016 Fig 11 above reflects the change in river flow in a standard year over a monthly period.

The lowest river discharge rate occurs during the dry period (summer and fall with averages of less than 0.5 m3/sec).

Due to the continuous low rainfall in summer and fall, the lowest point of streamflow

usually occurs in August. In order to study the trend of baseflow discharge rate, the seasonal mean streamflow data (July to Sep) from 1974 to 2010 is shown into the following line chart.

Fig 12. Mean Discharge Rate 1974-2010 in Fall season (July to Sep) According to Fig 12, there was a slight downward trend in baseflow discharge rate

between 1974 and 2010. The trend is consistent with the downward trend in summer and autumn total precipitation.

Fig 13. Monthly Precipitation and Discharge Rate Variations in 2016 Figure 13 shows a comparison between the monthly precipitation with the monthly

discharge for 2016. From the visual information in Fig 13, it is evident that during the rainy season, the rainfall and the stream flow of the salmon river equally high. This phenomenon occurs because rainfall supplements the surface water. However, during the dry season, the amount of precipitation dropped sharply, but the water level of the river did not change drastically, it decreased slightly from 1.7 m3/s to about 1.4 m3/s. Therefore, we can be inferred that the river was supplemented by groundwater to maintain baseflow during the summer and fall.

The data in Table 4 is from the Golder Associate and records the average hydraulically

inflow and outflow between Surface Water (Salmon River and Nicomekl River) and groundwater from the Hopington AB Aquifer from 1945 to 2012. The hydraulically inflow and outflow here do not include artificial withdraw and recharge.

4.3 Evapotranspiration ET is one of the main outputs in the predictive model, so it is very important to collect

accurate and reliable ET data. The table below is a normalized statistical table of daily ET data

from 2013 to 2017 detected by Langley Central Station (Environment Canada). The use of the monthly average total ET figures was used for the 2013 to 2017 period to represent the total monthly ET in the predictive model.

The location of the station: Latitude: 49°05'00.000" N Longitude:122°37'00.000" W.

Fig 14. Monthly Evapotranspiration Variation

Fig 15. Seasonal ET Pie Chart From the above data Tables and Figures, we can see that in winter and spring, the annual

total ET is small, while in summer and autumn, the value is larger. The average annual total ET for the past 5 years was 721.42 mm, with the average total ET for dry seasons (summer and autumn) being 578.12 mm. This means that 80% of the total annual ET is produced during this time period. On the contrary, less than 20% of the total annual ET is generated in the wet seasons. Such a pattern shows a negative correlation to annual precipitation.

4.4 Aquifer information

Since the groundwater resource in the Hopington AB Aquifer is not confined, the human activities need to be considered in terms of drinking water and irrigation water use. The water resources of the underground reservoir are mainly pumped from private wells and 4 municipal wells in the Township of Langley. These water uses for human activities include (1) water for human life, (2) water for agricultural activities, (3) water for livestock, (4) water for recreational activities etc.

For the calculation of effective precipitation and evapotranspiration, it is important to study different land uses within the region. It is assumed that only 10% of the precipitation in the urban land use can effectively be used to replenish the groundwater (Golder Associate Ltd. 2016), because the ground is mainly impervious, and most of the precipitation will transpire in the summer. For forest and agricultural land use, this project assumes that 65% of the precipitation can enter the unconfined aquifer, as part of the rainfall is preserved in the soil and does not enter the groundwater (Golder Associate Ltd. 2016).

Fig 16. Golder Interpretation of Hopington AB Aquifer Fig 16 shows the extent of the Hopington AB Aquifer given by Golder Associate. The land

use within the study area was divided into three categories. The three types of land use in the area are 1) urban land use, 2) forest land use, and 3) agricultural land use. The following table shows the area of the above three land uses and their percentages based on (Golder Associate Ltd. 2016).

Fig 17. Land use summary of the Hopington Aquifer in % area overlying the aquifer Due to the soil conditions and the ideal climate, the Township of Langley is a productive

agricultural municipality in Canada. Common agricultural sectors include berry and livestock production and many hobby farms that have sheep and horses.

4.5 Water usage In the Hopington AB Aquifer, groundwater extraction is mainly through private wells and

4 municipal wells. Based on the Township of Langley Water Management Plan (WMP, 2006)， the groundwater is mainly used for domestic purposes, irrigation, livestock use and minor commercial activities. Figure 18 (Water Service Department of Metro Vancouver) indicates that with the expanding population and growing GWD Service Population, the total water usage in Township of Langley has an upward trend (do not include Hopington AB aquifer water use). The Township of Langley became a member in Greater Vancouver Water District, and the annual water consumption has increased year by year, especially during the period from 2013 to 2017. The water consumption has increased sharply from an average of 22 ML / d in 2013 to nearly 38 ML / d. This data has almost doubled in five years. And the sharp increase in water consumption in the last 5 years is due to the increase of population.

Fig 18. Annual water use and population change in Township of Langley

Fig 19. Water use in Township of Langley per capita per day Figure 19 shows the changes in water use per capita in the Township of Langley. From this

we can see that from 1990 to 2017, the annual per capita water consumption is showing a downward trend. In 1990, the per capita water consumption was more than 700L /P/ d, but this was reduced to 300L /P/d by 2017 as a result of widespread water conservation efforts. This downward trend illustrates the effectiveness of the local water action plan to improve water efficiency.

The data in Table 8 above is from the Golder Associate. It reflects the average monthly

groundwater withdrawal from 1945 to 2012. In addition, due to the local government’s emphasis on decreasing groundwater use, the

Township of Langley set out a water management plan to “ensure safe and sustainable water for the community for generations to come”. For the Hopington Aquifer, the local government has currently set limitations and regulations on the private wells water extractions and land uses in the area to protect the unconfined aquifer. This means that the study area is under protection, but due to the growing population and urbanization land-use pressure, water demand is intense. I assumed that the population growth is currently limited but agricultural intensification is still putting pressure on the Hopington AB aquifer. I assumed that agricultural intensification will lead to an increase of about 10% of groundwater use over the next 10 years.

Part 5: Predictive model results

4.3 Results

According to the data collation and analysis in Part 3, the average monthly total

precipitation value is converted from the mm unit to the m3 unit by the aquifer size. The final value of the effective precipitation is calculated by the above effective precipitation calculation formula 3. The final results are present in Table 9.

By using the same processing method as the precipitation data to convert the unit mm

into unit m3.

The above table obtains the cumulative change of the water table by calculating the

total input and the total output respectively. The final result is shown in Figure 20 below.

Fig 20. Groundwater water table cumulative change line chart Fig 20 depicts the groundwater water table monthly changes over the annual cycle. In the

spring, the groundwater level in Hopington AB Aquifer is rising from January to June, the peak point will occur in March (148.27mm). After that, the line falling gradually in summer and falling below 0 mm in June and continues to show a downward trend in autumn. In September, the water level is predicted to reduce to the lowest water level, -268.20mm. Later, due to the heavy rainfall in winter, the groundwater level will begin to rise, and the groundwater level recovered to -59.70mm in December.

Overall, according to the model's predictions, the groundwater level of Hopington AB

aquifer will continue to decline at a rate of approximately 6 centimeters per year over the next few years. However, in the report of Township of Langley in 2002, the declining rate of the water table was 30 centimeters per year. This indicates that the Water Management Plan in Langley has shown an effective positive impact on mitigating the groundwater declining issue in the Hopington AB Aquifer area.

Scenario 1: Climate change effect

In part 3 of the analysis of the precipitation data the precipitation was changed to under the influence of the climate change by using the data from the historic trend analysis. The total precipitation in spring will rise slightly, while the rest of the three seasons will decline. Meanwhile, due to the climate change, ET values will vary in different seasons. According to the projection, in the wet reason, ET remains basically unchanged, while the values of ET in summer and fall will increase to some extent.

Based on the above analysis, reasonable assumptions are listed below. 1) The total precipitation in spring will rise by 5% and total precipitation in the remaining three seasons will fall by 5%.

2) In spring and winter, the ET values remain unchanged. In summer and fall, the ET values will increase by 5%.

3) The rest of the data does not change. The tables 12-14 below list the adjusted data based on the above assumptions.

Fig 21. Groundwater water table cumulative change line chart (Scenario 1) The line in the above Fig 21 shows the changes in groundwater water table annual

variation under Scenario 1. In the spring, the groundwater level of Hopington AB Aquifer is rising, reaching a peak point in March (160.71mm). After that, the line falling gradually in summer and falling below 0 mm in June and continues to show a downward trend in autumn. However, in September, the water level is predicted to be reduce to the lowest water level, -295.33mm. Later, due to the heavy rainfall in winter, the groundwater level will begin to rise, and the groundwater level recovered to -101.44mm in December.

Overall, according to the model's predictions, the groundwater level of Hopington AB

aquifer will continue to decline at a rate of over 10 centimeters per year over the next few years under the climate change effect. Scenario 2: Climate change effect & Population growth pressure

In addition to the impact of climate change, there are also pressures from population growth and urbanization in the region.

Due to the local government’s emphasis on decreasing groundwater, Township of Langley

set out a water management plan to “ensure safe and sustainable for the community for generations to come”. For the Hopington Aquifer, currently, the local government set limitations and regulations on the private wells water extractions and land uses in the area to protect the unconfined aquifer. Which means that the study area is under protection, but due to the growing population pressure. I assumed that the population growth and intensification of agricultural practices still poses pressure on Hopington AB aquifer. The pressure may lead to 10% increase on the groundwater outflow from pumping.

Based on the above analysis, reasonable assumptions are listed below. 1) The total precipitation in spring will rise by 5% and total precipitation in the remaining

three seasons will fall by 5%. 2) In spring and winter, the ET values remain unchanged. In summer and fall, the ET values

will increase by 5%. 3) 10% increase on the groundwater outflow from pumping. 4) The rest of the data does not change. The tables 15-17 below list the adjusted data based on the above assumptions.

Fig 20. Groundwater water table cumulative change line chart (Scenario 2) The line in the above Fig 20 indicates the groundwater water table annual variation over

one year under Scenario 2. In the spring, the groundwater level of Hopington AB Aquifer is rising, the peak point will occur in March (159.24mm). After that, the line falling gradually in summer and falling below 0 mm in June and continues to show a downward trend in autumn. However, in September, the water level is predicted to reduce to the lowest water level, -300.30mm. Later, due to the heavy rainfall in winter, the groundwater level will begin to rise, and the groundwater level recovered to -107.94mm in December.

Overall, according to the model's predictions, the groundwater level of Hopington AB

aquifer will continue to decline at a rate of about 8 centimeters per year over the next few years under the climate change effect and population growth pressure.

Part 5: Summary and Recommendations To sum up, from the average of previous years, the water level in Hopington AB Aquifer

is decreasing year by year. When faced with population growth pressures and reginal climate change impacts, the groundwater level declining rate will be significantly accelerated. At the same time, the salmon river baseflow in fall season will also decrease as the water table at Hopington AB aquifer decreases. The Hopington AB Aquifer was assessed to have the great risk and vulnerability to environmental factors. One positive finding is that despite the lowering of the water table in the aquifer, the groundwater contribution to the Salmon river flow has not declined.

To protect Hopington AB Aquifer, the recommendations are listed below. 1）Maintain the existing urban land use area ratio or reduce its land occupation ratio. Groundwater modelling indicates that the low effective precipitation ratio in urban land

use area significantly reduce the effective precipitation as a major input for the groundwater system.

2) Following the Water Resource Management Strategy (WRMS) to provide the Township

with a comprehensive approach for managing the quantity and quality of its local groundwater and surface water resources.

The Strategy’s 20-Year Action Plan is addressing these goals through three initiatives: 1)

public outreach, 2) studies, and 3) management options (Golder 2002). In 2002, Township of Langley launched a Water Wise program which informs residents of

the importance of local groundwater resources and provides practical information on how to protect drinking water. The major public outreach initiative is door to door visits by volunteers. Other public outreach initiatives include a low-flow rebate program for renovations, a water-wise garden contest, rain barrels, and water-saver kits. In addition to water conservation, the Water

Wise program educates the public about the importance of protecting groundwater quality (Township of Langley, 2007).

The Township of Langley is the first municipality in BC to develop a Water Management Plan, some new form of management and regulations is revised to prevent water conflicts and risks. Due to the vulnerable unconfined aquifers, especially Hopington AB Aquifer, the Township wants to address the groundwater declining issue as well as being proactive in protecting those aquifers that are currently uncontaminated (Watershed Watch Salmon Society, 2007).

3）Artificial recharge of Hopington AB Aquifer in summer and autumn will be necessary

because total precipitation in dry seasons will be lower as projected. The modelling indicates that this over-extraction has already caused base flows to decline

in Salmon River. In the Township of Langley, the stream flows that sustain salmonids and other fish are provided almost exclusively by groundwater during the summer months (Township of Langley 2004). So, in order to protect fish species in Salmon River and other hydraulically connected streams, artificial recharge is one of the most effective way to maintain the baseflow in dry seasons.

4）More stringent regulation for water use in private wells to prevent overuse of the Hopington AB Aquifer groundwater resource.

As aforementioned, the Water Management Plan is intended to address or prevent

conflicts between water users, and to protect and address the quantity and quality of groundwater supplies. This may include structuring the allocation of groundwater (i.e., requiring permits for its extraction), as well as creating new regulations to protect groundwater recharge, quantity and availability. Water users include fish, and the plan intends to assess the contribution of groundwater to base flows in specified fish-bearing streams. The contribution of wetlands to groundwater recharge will also be assessed, and recommendations made to protect groundwater base flows and recharge, in order to maintain suitable base flows for healthy fish habitat (Ministry of Environment 2006).

Limitations 1) I assumed no groundwater use for agriculture (because of lack of data). This could have

a significant effect on the water balance. 2) A 10% recharge potential from the urban area was used in the model calculation but

this could be significantly higher because most are rural residences have limited impervious areas and all have septic systems.

3) A sensitivity analysis of the model was not performed due to lack of time but should be considered in any future modelling efforts.

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