Long Point Region, Kettle Creek and Catfish Creek Integrated Water Budget
Total Page:16
File Type:pdf, Size:1020Kb
Long Point Region, Kettle Creek and Catfish Creek Integrated Water Budget Final Report April 2009 Prepared by LONG POINT REGION, CATFISH CREEK AND KETTLE CREEK INTEGRATED WATER BUDGET REPORT Executive Summary For the purposes of the Clean Water Act (MOE, 2006), a partnership was formed in 2004 between the Grand River Conservation Authority (GRCA), Long Point Region Conservation Authority (LPRCA), Catfish Creek Conservation Authority (CCCA) and Kettle Creek Conservation Authority (KCCA) to form the Lake Erie Source Protection Region. The four Conservation Authorities agreed to jointly undertake research, public education, and watershed planning and management for the advancement of drinking water source protection for the respective watersheds. This report documents the approach and findings of the Integrated Water Budget for the Long- Point Region, Catfish Creek and Kettle Creek Conservation Authority (LPRCA / CCCA / KCCA) Study Area. The Integrated Water Budget outlined in this document is meant to partially fulfill the requirements of the Province of Ontario’s Clean Water Act (2006), and follows the guidelines developed by the Province (MOE, 2007). A water budget, as described by the Province’s Water Budget Guidance Document (MOE, 2007), is an understanding and accounting of the movement of water and the uses of water over time, on, through, and below the surface of the earth. This Report implements the use of two coupled models, a continuous streamflow-generation model (GAWSER) and a steady-state groundwater flow model (FEFLOW), as well as a rigorous water demand estimation process. It provides an extensive and integrated understanding of hydrologic processes and water use in the Long Point Region, Catfish Creek, and Kettle Creek Conservation Authorities. The integrated manner in which the FEFLOW and GAWSER models have been calibrated to two independent data sets (1, total streamflow and baseflow and 2, water well levels) provides enhanced confidence in the model-predicted flow volumes. When assessing model performance, the use of multiple, but separate, datasets increases the confidence that the modelling system is accurately representing the hydrologic processes. Based on the overall performance of the modelling system in replicating these observed conditions, the modelling system is considered to be accurately replicating surface and groundwater flow volumes, and is thus appropriate to provide realistic water budget estimates for the Study Area. The Study Area was designated a “High Use Watershed” area by the Ontario Ministry of the Environment (MOE) in 2005 (AquaResource, 2005), based on a preliminary, regional assessment. The assessment contained within this current Integrated Water Budget Report, provides a more detailed and rigorous evaluation of water budget components throughout the Study Area. Subsequent watershed-wide studies included a Water Use study for each Conservation Authority (Bellamy and Wong, 2005), a draft Watershed Characterization study for each Conservation Authority (Lake Erie Source Protection, 2008), and a draft release of the Water Budget Report for the Study Area (AquaResource, 2008). Numerous other studies have examined individual areas and creeks within the Watersheds. The Integrated Water Budget Report was completed using a set of water budget tools (groundwater flow and streamflow numerical models). To simulate surface water flows and partitioning of precipitation, continuous hydrologic modelling was employed using the GAWSER models constructed for each Conservation Authority (Schroeter & Associates, 2006a, b, c). As part of this Integrated Water Budget Report, the GAWSER modelling included an enhanced approach to incorporating water takings and is able to simulate streamflows that reflect all seasonal hydrologic processes. By incorporating agricultural demand, the hydrologic modelling has provided improved characterization of that demand. To simulate groundwater flows, a regional-scale FEFLOW model was developed and calibrated to available water level and 8/17/2009 i FINAL REPORT LONG POINT REGION, CATFISH CREEK AND KETTLE CREEK INTEGRATED WATER BUDGET REPORT streamflow data. The original groundwater flow models (WHI, 2003 & 2007) were built upon in this Report to enhance modelling of key regional-scale features in the Study Area and to better represent bedrock characteristics. The FEFLOW model is designed to represent average annual groundwater flow conditions, with particular focus on volumetric flow from one subwatershed to another. Together these modelling tools provide a physical means of quantifying flows through the system for determining available water resources in the Study Area. Significant efforts were also undertaken to better quantify and characterize the consumptive water demand throughout the Study Area. The water demand characterization completed in this study included efforts to verify Permit-To-Take-Water (PTTW) information, gathering “actual pumping” data, estimating agricultural demand based on discussions with the farming community, validating actual use information through calibration of the surface water model, and gathering relevant information contained within MOE’s PTTW paper files. The improved understanding of water demand provides an enhanced ability to characterize the water demand throughout the Study Area. The Tier 2 Water Quantity Stress Assessment was prepared as a companion document to this report (AquaResource, 2009a) as a structured means of evaluating the degree of potential water quantity stress throughout an area by comparing the volume of water demand to that which is practically available for use. The results of streamflow and groundwater flow modelling and water demand estimates from this Integrated Water Budget were incorporated into the Tier 2 Water Quantity Stress Assessment to fulfill the requirements of the MOE’s Technical Rules (2008). Using predetermined thresholds for hydrologic stress, subwatersheds were classified as having a Low, Moderate, or Significant potential for stress. As per the Clean Water Act Technical Rules (MOE, 2008), municipal water systems located within a Tier 2 potentially stressed subwatershed meet the requirements to proceed with a Tier 3 Water Quantity Risk Assessment. Integrated Water Budget The continuous streamflow model (GAWSER) and the steady-state groundwater flow model (FEFLOW) used for this Report were integrated using the groundwater recharge parameter and through calibration to the same baseflow discharge data. The GAWSER model was initially calibrated / verified to streamflow observations, with estimated groundwater recharge values subsequently provided to the groundwater flow model as input. The groundwater flow model was then calibrated to observed water levels and baseflow estimates. Having such a coupled modelling system, calibrated to two independent data sets (streamflow and groundwater levels), increases the level of confidence in both models and allows an integrated set of water budget parameters to be produced, as given in the following Table. 8/17/2009 ii FINAL REPORT LONG POINT REGION, CATFISH CREEK AND KETTLE CREEK INTEGRATED WATER BUDGET REPORT Value Value Water Budget Parameter (m3/s) (mm/year) Precipitation 115.6 953 Evapotranspiration 67.3 555 Runoff 23.5 194 Recharge 24.8 204 SW Taking 0.9 7 Net Groundwater Discharge to Surface Water Features 20.0 164 GW Taking 1.7 14 The numeric models developed for this Study are regional in nature. They provide an improved understanding of the flow characteristics for both surface water and groundwater flows at that scale and discussion on a subwatershed basis in the Report details the enhanced understanding derived from the models. Local-scale features may not be well represented in the models and, therefore, results of the models should be interpreted at the scale for which they were designed. Beyond the water budget, this report provides an enhanced understanding of the flow system using forward particle tracking, which illustrates the linkages between recharge areas and discharge areas. This knowledge will help water managers to better understand potential impacts of future changes to the landscape throughout the Study Area. 8/17/2009 iii FINAL REPORT LONG POINT REGION, CATFISH CREEK AND KETTLE CREEK INTEGRATED WATER BUDGET REPORT TABLE OF CONTENTS 1.0 INTRODUCTION .................................................................................................. 1 1.1 THE CONSERVATION AUTHORITIES................................................................ 1 1.1.1 Long Point Region Conservation Authority.................................................................1 1.1.2 Catfish Creek Conservation Authority.........................................................................2 1.1.3 Kettle Creek Conservation Authority...........................................................................2 1.2 SIGNIFICANCE OF WATER USE IN THE WATERSHEDS................................. 2 1.3 SCOPE OF CURRENT ASSESSMENT ............................................................... 2 1.4 SCALE OF ASSESSMENT .................................................................................. 3 1.5 METHODOLOGY ................................................................................................. 3 1.5.1 Water Use Estimates ..................................................................................................4 1.5.2 Continuous Surface Water Model (GAWSER) - Background.....................................4 1.5.3 FEFLOW Model