ENVGEO362 Lecture 2 Fall 2024 PDF

Natural resource management 2. Water resource management Some physical aspects of water resources Water resources and their uses Main sources: – Physical Geography, Strahler & Archibold – Textbook chapter 14 Intro: the cycling of water on the continents As water is a mobile resource, it is import...

Natural resource management 2. Water resource management Some physical aspects of water resources Water resources and their uses Main sources: – Physical Geography, Strahler & Archibold – Textbook chapter 14 Intro: the cycling of water on the continents As water is a mobile resource, it is important to have a good understanding of some physical aspects of water resources. Earth's water: what is where? Spheres showing available quantities globally: (1) All water (sphere over western U.S., 860 miles in diameter), (2) Fresh liquid water in the ground, lakes, swamps, and rivers (sphere over Kentucky, 169.5 miles in diameter), (3) Fresh-water lakes and rivers (sphere over Georgia, 34.9 miles in diameter). Source: http://water.usgs.gov Intro: the cycling of water on the continents Source: Reviews of Geophysics Volume 50, Issue 4, RG4003, 8 NOV 2012 DOI: 10.1029/2012RG000389 http://onlinelibrary.wiley.com/doi/10.1029/2012R G000389/full#rog1750-fi g-0001 Oceanic and terrestrial sources of continental precipitation (average annual water flows in 1,000 km³) Estimates of the - observed main water reservoirs (black numbers, in 10 3 km3) and the - flow of moisture through the system (red numbers, in 10 3 km3 yr−1). Adjusted from Trenberth et al. [2007a] for the period 2002–2008 as in Trenberth et al.. Intro: the cycling of water on the continents In terms of management of water resources, the focus is primarily on the surplus of land precipitation over evaporation over land. – infiltration of water from rainfall in soils, temporarily held as soil water (soil moisture) – runoff: e.g. when rain falls too rapidly to pass into the soil – evapotranspiration: evaporation from the soil and transpiration – percolation: slow movement under the influence of gravity beyond the soil water belt to groundwater (here: pore spaces in the bedrock or regolith completely filled with water) → water table = top of the saturated zone Intro: the cycling of water on the continents – water table: highest under hills/elevated land surfaces, vs lower in valleys – lakes, ponds, marshes: where the water table intersects the surface: – very slow flow rate of subsurface water – water table raises because of downward percolation, and lowers because of seepage into lakes and streams Intro: the cycling of water on the continents – aquifers: underground layer containing abundant, freely flowing groundwater (e.g. layers of sand or sandstone); porous rock saturated with water – aquitards: hold little water, relatively impermeable (e.g. layers of clay and shale) – where impervious rock is overlain by porous rock, groundwater can freely move through the aquifer and cause springs Problems of groundwater management Rapid withdrawal of groundwater has seriously affected the environment in many places: – Increased urban populations and industrial developments require larger water demands → new wells (affecting groundwater), or using more and more surface water – Agriculture in dry climates is heavily dependent on irrigation water from pumped wells (especially since major river systems are likely to be already fully used for irrigation) Agriculture near Taber, AB Problems of groundwater management * water table depletion (when depletion exceeds infiltration) – water level in the well drops – surrounding water table drops in the shape of a downward- pointing cone (cone of depression) Problems of groundwater management * contamination of groundwater: pollutants – contamination of wells by pollutants that infiltrate the ground and reach the water table can be a major environmental problem arising from groundwater withdrawal (e.g. Walkerton 2000) – disposal of solid wastes can pose a major environmental problem in developed countries because their advanced industrial economies provide an endless source of garbage Problems of groundwater management * contamination of groundwater: saltwater intrusion in coastal wells – a layer of salt water from the ocean may lie under a coastal fresh water aquifer (fresh water is less dense than salt water) – as the freshwater aquifer is depleted, the level of salt water rises and eventually reaches the well from below, making the well water unusable Source: https://www.usgs.gov/mission-areas/water-resources/science/saltwater-intrusion Stream flow and flooding By Shannon1 - Own work, CC BY-SA 4.0, https://commons. wikimedia.org/w/i ndex.php? curid=83615743 Changes in the discharge of a large river (North Saskatchewan River), for one specific year, at Prince Albert, SK - watershed of appr. 130K km2 Note: data can be retrieved via https://wateroffice.ec.gc.ca/index_e.html Stream flow and flooding Hydrographs of larger streams show the effects of - base flow (seepage of groundwater into the channel) - direct input (runoff) E.g. the hydrograph of the North Saskatchewan River in Prince Albert: - Dec-Ma: mainly groundwater seepage (as snowpack covers the drainage basin) - Ma-Apr: first peak due to snow melt on the Prairies - June: later melt of large snowpack in headwaters near the Rockies (+ lag time), increasing groundwater storage and base flow - Aug/Sept: occasional rainstorms - Nov: cold snap sets ice on the river and reduces discharge Q: How does this annual flow cycle impact irrigation? Q: How can global warming have an impact here? Stream flow and flooding River Floods = when the discharge of a river cannot be accommodated within its normal channel e.g. in Ontario: - localized high intensity short duration rainfall (often associated with severe thunderstorms) - ice jams (e.g. spring break up) Note: in Ontario also often shoreline flooding related to high water levels/high winds on the Great Lakes https://www.cbc.ca/news/canada/kitchener- waterloo/grca-flood-warning-entire-grand- river-watershed-1.5424109 Stream flow and flooding Flood plain: broad belt of low, flat ground bordering a river channel that floods regularly; typical for most low-gradient rivers of humid climates Source: https://trca.ca/conservation/flood-risk-management/defining-flood-risk/ Stream flow and flooding Fig: Precipitation and stream flow for a 800 km2 drainage basin in Ohio, following a heavy summer rainstorm. Stream flow A stream’s discharge increases in response to a period of heavy rainfall (or snow melt). Delayed response: – lag time = difference between the time when half of the precipitation has occurred and the time when half the runoff has passed downstream Stream flow and flooding – the delay depends e.g. on the size of the drainage basin feeding the stream; larger drainage basins show a longer delay – flash floods: short lag times (characteristic of streams draining small watersheds with steep slopes); stream can quickly rise to a high level, sometimes accompanied by great quantities of course rock debris swept by the flood water Stream flow and flooding Magnitude of a flood = peak discharge (or highest stage) of the river during flooding Historical and real time data help to: - understand the river’s previous behaviour - monitor changes to predict the onset of a flood Canadian federal and provincial agencies coordinate the forecasting from regional centres across the country: - analyze precipitation patterns - analyze progress of high waters moving downstream - compare with flood history of the specific river → specific flood forecasts Stream flow and flooding e.g. in this location, what is a 5-year flood? a 600 m3/s maximum annual flood can be expected on average every 5 years here (aka a 5-year flood) a 100-year flood? flood event that has on average a 1/100 chance (1% probability) of being equaled or exceeded in Fig.: flood frequency data for the Lillooet River at Pemberton, BT. Each dot is a measured yearly any given year. discharge in an 88-year record. Note: these are probabilities: a five-year flood can be followed the next year by another five-year flood... Assessing Canada’s water resources Q: Some countries in the world are water poor; they cannot afford the cost of sustainable clean water to all people at all times. - Would you consider Canada water rich or water poor in comparison to the rest of the world? - Which data would you need to realistically assess this? https://cropinno.com/2022/08/06/ https://www.country1053.ca/2019/09/27/ drought-in-canadian-farms/ new-nature-trail-in-big-trout-bay/ Water resources and their uses Source: https://tableau.apps.fao.org/views/ReviewDashboard-v1/country_dashboard? %3Adisplay_count=n&%3Aembed=y&%3AisGuestRedirectFromVizportal=y& %3Aorigin=viz_share_link&%3AshowAppBanner=false&%3AshowVizHome=n Water resources and their uses Source: https://tableau.apps.fao.org/views/ReviewDashboard-v1/country_dashboard? %3Adisplay_count=n&%3Aembed=y&%3AisGuestRedirectFromVizportal=y& %3Aorigin=viz_share_link&%3AshowAppBanner=false&%3AshowVizHome=n Water resources and their uses Source: https://www150.statcan.gc.ca/ n1/en/pub/11-627-m/11-627- m2022087-eng.pdf? st=LaSGRQqz Water resources and their uses Source: https://www.canada.ca/en/environme nt-climate-change/services/environm ental-indicators/water-withdrawal- consumption-sector.html - some sectors have high consumption of water used (e.g. agriculture and oil and gas); - other sectors return most of the water withdrawn (e.g. thermal power generation) Source: https://www15 0.statcan.gc.ca /n1/daily-quoti dien/170321/g- b001-eng.htm Assessing Canada’s water resources - Average precipitation in Canada: 600 mm annually (a bit less than the average worldwide) -Average runoff (renewable): 330 mm annually (runoff: precipitation that eventually flows into rivers and streams) - Canada: 7% of the world's renewable runoff (one of the highest total renewable water resources per capita worldwide) - Canada: on top of this also a lot of non-renewable water resources, totaling 20% of the world's total freshwater supply (e.g. only 1% of water supply of the Great Lakes is renewed on an annual basis). - but: looking at the total amount does not tell the whole story; assessing Canada’s water resources needs to be based on more than just the total amount: the volume available is very diverse from region to region, the variability changes throughout the year, the importance for ecosystems, water quality,... Assessing Canada’s water resources (a) volume available in specific places: runoff in parts of the southern prairies less than 50mm/yr vs. 2.000+mm/yr in parts of BC Source: https://www150.statcan.gc.ca/ n1/daily-quotidien/170321/mc- b001-eng.htm Assessing Canada’s water resources (b) variability: - times of year when it is available (in parts of the country where stream flow is linked strongly to snowmelt, the majority of total annual flow occurs in spring, e.g. Saskatchewan River Basins in southern Alberta: most of the stream flow in May and June) - variability from year to year (e.g. 1.7 billion to 13.2 billion m³/year flow volume in the river described). See e.g. annual changes in the amount of water flowing in Canada's rivers (2001-2019) at https://www.youtube.com/watch?v=6XcMWiNYy04&t=51s Natural ecosystems are adapted to this variability, but human societies are at risk from too little/too much --> humans have become adept at controlling when and where water flows e.g. using dams and reservoirs, esp. in southern Canada Assessing Canada’s water resources (b) variability: - data on runoff and precipitation (knowing the frequency of high and low flows during the last 30 years): allows water managers to make meaningful assumptions about future water availability (based on “stationarity” = statistical concept that allows/allowed planners to assume that the future will be similar to the past) - however, variability will increase due to climate change: timing of precipitation, means and extremes of precipitation, evapotranspiration, rates of discharge of rivers … → the past will no longer be a reliable guide to the future; water management will become more difficult as uncertainty increases aka “death of stationarity” Assessing Canada’s water resources (c) importance for ecosystems: Withdrawals of surface water/groundwater (especially when withdrawals increase during dry periods) --> can affect base flow in streams and rivers (since the base flow is supported by groundwater discharge), especially important in drier summer months --> reduced base flows also means reduced surface water flows in streams and rivers; this affects the quality of aquatic habitats, or leaves insufficient flows in rivers for dilution of wastewater treatment plant effluent,... Assessing Canada’s water resources (d) water quality: Water pollution through point sources (e.g. sewage, industrial discharge), or non-point sources (e.g. agricultural runoff) - phosphorous (e.g. runoff from farm fields) can accelerate eutrophication, algae, reducing dissolved oxygen levels, and degrading habitat quality for fish/aquatic organisms - industrial discharges, atmospheric deposition: toxic substances e.g. heavy metals, PCBs - water pollution can also threaten human health, e.g. Walkerton case (see textbook p. 351): runoff from livestock farm → municipal well → 7 casualties and 2K+ seriously ill → complete overhaul of Ontario’s approach to drinking water safety e.g. (boiling) water advisories in many First Nations communities, see e.g. https://www.sac-isc.gc.ca/eng/1506514143353/1533317130660 Assessing Canada’s water resources (e) human use and activities Human activities stress the - quality of (ground)water: groundwater can be contaminated from leaking underground storage tanks, chemical spills, urban and rural land-use practices - quantity of groundwater: - about ¼ of Canadians rely on groundwater for drinking water - appr. 40% of agricultural water (and some of the industrial water as well) is supplied by groundwater Climate change gives significant extra concerns: - quantity concerns (reductions) for many parts of the country - quality concerns: increased surface temperatures, reduced assimilative capacity, saltwater intrusion in aquifers in coastal areas