18-Env-B2 Water Resources · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2016 — 04-Env-B2 / Water Resources. 3 hours duration; closed book; Casio or Sharp approved calculator only. Six Problems are printed; any five constitute a complete paper (the first five answered are marked). Each Problem is worth 20 marks. All six are solved below for completeness.
Reference texts. Linsley, Kohler & Paulhus, Hydrology for Engineers (3rd ed.); Chow, Open-Channel Hydraulics; Freeze & Cherry, Groundwater; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); Ontario Ministry of the Environment, Stormwater Management Planning and Design Manual (2003); Fisheries Act, Ontario Water Resources Act, Clean Water Act, 2006 (Ontario).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Water Resources Sustainability is the management, allocation, and protection of surface water and groundwater resources so that present human, economic, and ecological needs are met without compromising the ability of future generations to meet their own needs from the same resource. It requires that water be used at a rate, and returned at a quality, that the natural hydrologic cycle can indefinitely replenish and assimilate — balancing environmental integrity, social equity, and economic viability (the classic sustainability "triple bottom line") over multi-decade planning horizons rather than optimizing for the next budget cycle alone.
At least six facts must be weighed together when planning for water resources sustainability:
| # | Consideration | Why it matters |
|---|---|---|
| 1 | Sustainable yield | Withdrawals (surface or groundwater) must not exceed the long-term natural recharge/replenishment rate, or storage is permanently mined. |
| 2 | Water quality & assimilative capacity | Pollutant loading to a receiving water must stay within its capacity to dilute/assimilate contaminants without degrading beneficial uses. |
| 3 | Environmental (in-stream) flow needs | A minimum flow regime must be preserved to sustain aquatic habitat, fish passage, and downstream ecosystems, not just the human abstraction. |
| 4 | Climate variability and change | Shifting precipitation patterns, reduced snowpack, and more frequent droughts/floods must be built into supply and infrastructure planning. |
| 5 | Population growth & land-use change | Urbanization increases both demand and impervious cover, simultaneously raising withdrawal needs and cutting natural groundwater recharge. |
| 6 | Integrated, watershed-based governance | Multiple competing uses (municipal, agricultural, industrial, recreational, Indigenous, ecological) and overlapping federal/provincial/municipal jurisdictions must be coordinated at the watershed scale. |
| 7 | Infrastructure & economic sustainability | Full-cost pricing and reinvestment in aging treatment/distribution/collection assets are needed or the physical system itself becomes the limiting factor. |
| 8 | Intergenerational equity | Decisions taken today (over-allocation, contamination) must not foreclose options for future generations — the defining test of "sustainability" itself. |
Translating the definition above into practice is difficult because several forces work against it simultaneously. Climate change is altering the timing and magnitude of supply — earlier snowmelt, reduced summer baseflow, and more intense storm events all make historical hydrologic records a poorer guide to future design conditions, undermining both water-supply security and flood-control infrastructure sized on the old record. Population growth and urbanization compound this on the demand side: more people need more water while the same urban expansion pave over the recharge areas that replenished the resource, and increases the volume and rate of stormwater runoff that must now be managed.
Aging and undersized infrastructure is a distinct and growing challenge — many North American water, wastewater, and stormwater systems were built in the mid-20th century and now suffer from water loss (leakage), combined sewer overflows during wet weather, and capacity shortfalls that force expensive retrofits rather than allowing proactive planning. Fragmented governance and competing uses add a further layer: water resources rarely respect political boundaries, so a single watershed may be regulated by federal fisheries protection, provincial permits-to-take-water, municipal stormwater bylaws, and Indigenous rights and title all at once, and reconciling agricultural, industrial, municipal, recreational, and ecological demands for the same finite supply is inherently contentious.
Finally, diffuse (nonpoint-source) pollution from agricultural runoff and urban stormwater is far harder to regulate and treat than a single end-of-pipe discharge, funding and monitoring gaps mean many jurisdictions still lack full-cost water pricing or adequate groundwater-level/quality monitoring networks to detect problems early, and public awareness and political will for the long-horizon investment sustainability requires often lags behind more visible, shorter-term priorities. Overcoming these challenges is the core justification for integrated water resources management (IWRM) as a planning framework.
