Hydrology and Hydrogeology, SAIT, Winter 2025 PDF

GEOL 350 Hydrology and Hydrogeology Winter 2025 Aquifers © 2021, Southern Alberta Institute of Technology 2 Groundwater flow paths Aquitard Flow paths may be localized (shallow, shorter), intermediate, or...

GEOL 350 Hydrology and Hydrogeology Winter 2025 Aquifers © 2021, Southern Alberta Institute of Technology 2 Groundwater flow paths Aquitard Flow paths may be localized (shallow, shorter), intermediate, or regional (deeper, longer). Different flow paths takes groundwater through different geological layers, with implications for the chemistry of the groundwater. © 2021, Southern Alberta Institute of Technology 3 Figure 5.1 shows that groundwater flow may take place over short distances and time spans (local flow) or long distances and time spans (regional flow). https://static.ags.aer.ca/files/document/INF/INF_140.pdf -> deeper © 2021, Southern Alberta Institute of Technology 4  Water Table is connected to surface waters Groundwater can flow up (USGS, 1998) (USGS, 1998) The Water Table “meets” the surface at a water body (pond, lake, or stream). Both the elevation of the Water Table and the elevation of the top of the lake are dynamic and can change in response to one another © 2021, Southern Alberta Institute of Technology 5 Types of streams (Source of images: USGS, 1998) © 2021, Southern Alberta Institute of Technology 6  Interactions between stream and GW Depending on the relative magnitude of increases in stream stage, some streams and adjacent shallow aquifers may be in a continuous re-adjustment from interactions related to bank storage and overbank flooding (which facilitates recharge) Other processes may affect the local exchange of water between streams and adjacent shallow aquifers, like pumping a well that is near to a stream Some sediments can be deposit at riparian zone through runoff (USGS, 1998) © 2021, Southern Alberta Institute of Technology 7  Importance of the hyporheic zone (USGS, 1998) Hyporheic zone is a unique interface environment with enhanced microbial activity, chemical transformations, and abundant aquatic insects. High O2 concentrations in this zone allows organisms to live in the pore spaces in the sediments, thereby providing a refuge for those organisms (e.g. fish eggs) © 2021, Southern Alberta Institute of Technology 8 GW contribution to streamflow The contribution of groundwater to a stream’s flow is called baseflow Note that the streamflow is variable, related to precipitation events. However, the baseflow is more stable (USGS, 1998) © 2021, Southern Alberta Institute of Technology 9 Measuring baseflow in streams: Data from stream-gauging stations Plot on a hydrograph (flow volume vs. time) Baseflow is about 30% of total surface drainage across the study area (ECC) (? What do we call the rest of the surface drainage? Run-off) © 2021, Southern Alberta Institute of Technology 10 Groundwater and Aquifers © 2021, Southern Alberta Institute of Technology 11  With growing demand from development, our surface water resources are being strained. More and more, we will need to turn to 2011. The Energy Resources groundwater Conservation sources to meet Board/Alberta growing water Geological Survey (ERCB/AGS) needs © 2021, Southern Alberta Institute of Technology 12 Major River basins (watersheds) of Alberta A watershed is “a land area that channels rainfall and snowmelt to creeks, streams, and rivers, and eventually to outflow points such as reservoirs, bays, and the ocean” (National Ocean Service, n.d). It is also referred to as a drainage basin or catchment Watersheds are nested systems (small watersheds are nested into larger ones) https://www.youtube.com/watch?v=9isAx64IiSc © 2021, Southern Alberta Institute of Technology 13 © 2021, Southern Alberta Institute of Technology 14 Paskapoo outcrop…aquifer?? More Cemented layer Source: Edmonton – Calgary corridor groundwater atlas © 2021, Southern Alberta Institute of Technology 15  Groundwater movement in aquifers Groundwater movement is driven by differences in the elevation of hydraulic Above deposit, lots of erode happens up, heads in the subsurface. The hydraulic Then glaciers settling in above eroded layer. head is the level that groundwater rises to within a well. Hydraulic head is a measure of the potential energy that drives the flow of groundwater. Groundwater flows from areas with higher hydraulic-head elevations to areas with lower hydraulic-head elevations to equalize the water pressures between the two areas. Groundwater flow systems and hydraulic- head elevations are influenced by natural factors (drought or flooding) or by man- made stresses (groundwater pumping or alteration of the land surface). Source: ECC GW Atlas Paskapoo formation Effluvial movement © 2021, Southern Alberta Institute of Technology 16  Groundwater movement in aquifers Groundwater follows the path of least resistance through the subsurface, influenced by the geological layers’ properties, such as: geometry (orientation and shape of the layer), porosity permeability Groundwater flow can: be local to regional in scale; be constrained horizontally by boundaries known as groundwater divides: be constrained vertically or horizontally by impermeable layers (aquitards); contain one or more recharge and/or discharge areas. Outcrop of the Paskapoo formation – major aquifer in Source: ECC GW Atlas Alberta © 2021, Southern Alberta Institute of Technology 17 Xsection – source: ECC GW Atlas Check your understanding: 1.how many different aquifers do the wells test? 2.How many are unconfined? 3. How many are confined? 4. Can GW flow up? © 2021, Southern Alberta Institute of Technology 18  Geo data sources Logging core, measuring outcrop, groundwater sampling Source: GW Atlas © 2021, Southern Alberta Institute of Technology 19 Data from Airborne geophysical surveys Airborne resistivity or electromagnetic) surveys – measure the electrical properties of the sediments and water within the pores of the sediments. Interpretation of the data helps to map sediment types and characteristics of the water in the sediments With different tools, different depths in the subsurface can be investigated. Tools emit an EM pulse at a set frequency. Pulse travels downward into the ground and the return signal is recorded by a tool towed behind the aircraft. Source: GW Atlas © 2021, Southern Alberta Institute of Technology 20 Bedrock Geology of Alberta sourceECC GW Atlas © 2021, Southern Alberta Institute of Technology 21 sourceECC GW Atlas © 2021, Southern Alberta Institute of Technology 22  Bedrock Topography Mapping the bedrock surface is the boundary between consolidated sediments (bedrock) and unconsolidated sediments (which lie on top of the bedrock). In the groundwater model, this surface can define the boundary between different groundwater-flow patterns. Several factors have significantly altered the bedrock topography from its original state: (1) chemical weathering and especially (2) physical erosion (including erosion due to the advance and melting of glaciers during the most recent glacial period,which ended about 12,000 years ago) The bedrock topography shows three channel complexes or paleochannel complexes. This means that they are remnants of ancient river channels cut into the bedrock, later buried by younger sediments. © 2021, Southern Alberta Institute of Technology 23 Buried Valley Aquifers © 2021, Southern Alberta Institute of Technology 24 Great online Resource Check out: The Groundwater Project (https://gw-project.org/) Ebooks Exercises Videos Animations Models, interactive education tools, and associated problems © 2021, Southern Alberta Institute of Technology 25 References Barker, A.A., Riddell, J.T.F., Slattery, S.R., Andriashek, L.D., Moktan, H., Wallace, S., Lyster, S., Jean, G., Huff, G.F., Stewart, S.A. and Lemay, T.G., (2011): Edmonton–Calgary Corridor groundwater atlas; Energy Resources Conservation Board, ERCB/AGS Information Series 140. Winter, Thomas C., et. al. (1998). Ground Water and Surface Water: A Single Resource. U.S. Geological Survey (Circular 1139), Denver, Colorado. U.S. Department of the Interior. Lemay, T.G. and Guha, S. (2009): Compilation of Alberta groundwater information from existing maps and data sources; Energy Resources Conservation Board, ERCB/AGS Open File Report 2009-02. Sear, David A. Newson, Malcolm D. Thorne, Colin R.. (2010). Guidebook of Applied Fluvial Geomorphology. ICE Publishing. Retrieved from https://app.knovel.com/hotlink/toc/id:kpGAFG0003/guidebook-applied- fluvial/guidebook-applied-fluvial © 2016, Southern Alberta Institute of Technology. All rights reserved. This publication and materials herein are protected by applicable intellectual property laws. Unauthorized reproduction and distribution of this publication in whole or part is prohibited. Great online Resource Check out: The Groundwater Project (https://gw-project.org/) Ebooks Exercises Videos Animations Models, interactive education tools, and associated problems Water Table Recharge determines GW Divide and flow rate and direction) https://gw-project.org/interactive-education/wtr-water-table-recharge/ Well Capture sets various parameters to display a plan view of a well capture zone to consider contamination risk (https://gw-project.org/interactive-education/well-capture/) © 2021, Southern Alberta Institute of Technology 27 EXTRA SLIDES © 2021, Southern Alberta Institute of Technology 28 Bedrock Geology Map Look at strat chart (notice geological ages) and the pattern on the map. Why is the map pattern like it is, do you think? Erosion, tilt of the beds (which way?) © 2021, Southern Alberta Institute of Technology 29 Video animation of GW contamination from a surface spill https://gw-project.org/videos/ animation-of-the-life-cycle-of-a- dnapl-spill/ © 2021, Southern Alberta Institute of Technology 30 hydrochemistry Hydrochemistry is the study of chemical reactions and conditions in groundwater. Water interacts with the underground environment by dissolving solids and gases or by forming solids, causing changes to the chemical composition of the water. When we analyze and interpret groundwater’s chemistry, we learn from where the water came; through which type(s) of materials it has travelled and for how long; and if it has mixed with other types of water. Hydrochemistry helps us complete the groundwater model of the ECC by filling in details about how groundwater moves through the underground system. Knowledge of groundwater chemistry is also important when we want to decide which groundwater is suitable for drinking, agriculture or industrial use. The first control on groundwater chemistry is the source of the water in the groundwater system. Water that makes up the shallow groundwater system largely comes from precipitation that falls on the land surface as rain or snow. The properties of rain and snow can dissolve and alter the geological materials they contact as they move from the land surface down to the water table. These reactions change the chemistry of the water and the geological materials. Once water that recharges the groundwater system moves below the water table, it mixes with the existing water in the subsurface, making mixing an important consideration as we evaluate water chemistry. Dissolution reactions continue to occur below the water table, but increasingly, other types of water-rock interactions happen as water moves from its recharge zone toward its discharge zone. The amount of dissolved material in the water typically increases along the flow path and with depth, and the types and amounts of constituents typically change as well. Total dissolved solids express the quantity of dissolved minerals in a sample of water. Hardness is a property of water that causes residue to form when the water is used with soap or forms a deposit when water evaporates. Water hardness is determined by a combination of calcium and magnesium concentrations but is expressed as hardness as CaCO3 a quality-control assessment, called a charge balance, on the analyses. The charge-balance calculation lets us know if the electrical contributions of cations (positively charged parameters) and anions (negatively charged parameters) are nearly equal in the water sample. In theory, cations and anions must balance in all solutions. Therefore, to account for reasonable errors in analysis practices, we accepted charge balances that were within +/- 5% of neutral. © 2021, Southern Alberta Institute of Technology 31 Our first step in mapping the ECC’s hydrochemistry was to choose from which of the ECC’s geological units each analysis came. To do this, we considered well locations and the depths of the well screens, and we used the geological model that we had constructed previously. split the analyses based on which geological unit they came from, we analyzed each set of chemical constituents Specific reasons for the trends we see are related to the chemical composition of the geological materials that the water flows through, as well as the grain size of the sediments, which affects how easily water can move through the sediments. As a general principle, the longer the water remains in contact with geological materials, the more the water can react with those materials, changing the composition of the water and of the geological materials in the process. The Alberta Government considers groundwater with total dissolved solids of more than 4000 milligrams per litre (mg/L) to be saline (salty water). Total dissolved solids concentrations are generally less than 1500 mg/L except in certain areas south and east of Edmonton, and in the southernmost portion of the study area. © 2021, Southern Alberta Institute of Technology 32 © 2021, Southern Alberta Institute of Technology 33  Hydrology - Water Balance Water balance refers to water’s overall movement in and out of an area. To understand the ECC’s water balance, we did a hydrological study using a simple water-balance equation. This showed the importance of each of the ECC’s hydrological processes in the overall water balance. Water-Balance Equation The overall water- balance equation we used states that the change in the amount of water (surface water and groundwater), on a yearly basis, must equal the amount of precipitation, surface water and groundwater flowing into the ECC minus the amount of evapotranspiration and the amount of water flowing out of the area (surface water and groundwater). We can assess the change in how much water is stored in an area’s surface-water bodies and groundwater by subtracting all of the water leaving the area from the precipitation and groundwater the area receives. This water- balance equation helps us understand the average hydrological conditions across the ECC. In this equation, we assume that the total volume of surface water and groundwater stored in the ECC does not change from year to year. We find that, because the ECC is in an almost water-neutral area, small differences between precipitation and evapotranspiration © 2021, Southern Alberta drive Institute the of Technology 34 hydrological Contamination of GW GW can transport contamination from a point source and cause contamination of the river (USGS, 1998) © 2021, Southern Alberta Institute of Technology 35 Types of springs (USGS, 1998) © 2021, Southern Alberta Institute of Technology 36  Effect of a pumping well near a stream Pumping a water well near a stream can create a groundwater divide and intercept some of the GW that would otherwise discharge to the stream (USGS, 1998) © 2021, Southern Alberta Institute of Technology 37