Natural Infrastructure Essentials: A focus on water retention

This policy brief by the International Institute for Sustainable Development (IISD) examines the decline of water storage in the Canadian Prairies and advocates for natural water retention measures to mitigate the risks of floods and droughts exacerbated by climate change.

• The Canadian Prairies have experienced a significant decline in water storage capacity due to historical and ongoing drainage and altered landscapes. In Alberta, the loss of approximately 133,000 hectares of wetlands over 40 to 60 years resulted in a loss of roughly 379 million m³ of water storage capacity, which is about 21 times the volume of Calgary’s Glenmore Reservoir.
• Water retention is defined as the ability of a landscape to capture, store, and gradually release snowmelt and rainfall. It encompasses both natural measures, such as conserving and restoring floodplains, grasslands, riparian areas, and wetlands, and technical solutions like constructing small reservoirs. This approach differs from grey infrastructure, such as dry dams, which are designed for short-term water detention rather than long-term storage and do not provide the same broad co-benefits.
• Constructed water retention projects are increasing in popularity across the Prairies. In Alberta, Ducks Unlimited Canada manages 1,690 basins holding an estimated 1.6 billion m³ of water. In Manitoba, watershed districts built 257 projects between 2018 and 2023, providing 6.7 million m³ of storage. In Saskatchewan, Ducks Unlimited Canada restored drained wetlands across 3,842 acres using "ditch plugs."
• Water retention projects provide diverse environmental and economic benefits. These include reducing flood risk (e.g., the Steppler Dam in southern Manitoba reduced annual peak flows from snowmelt by 72% and summer rainfall by 48%), increasing water supply (e.g., Pelly’s Lake in south-central Manitoba), and improving water quality. A research site near Morden, Manitoba, showed average reductions of ~65% for peak flow, ~80% for total dissolved phosphorus, ~78% for total phosphorus, and ~82% for total suspended solids between 2016 and 2019.
• Water retention supports carbon sequestration and biodiversity. In the prairie pothole region, wetlands store an average of 205 t/ha of carbon, while 89 t/ha would be released if drained. Additionally, restored wetlands in Saskatchewan agricultural land showed similar water chemistry and abundance of macroinvertebrates and submersed aquatic plants to natural wetlands about 10 years post-restoration.
• Water retention projects offer economic advantages; a review of 10 projects in Southern Manitoba indicated that every dollar invested provided CAD 3.16 in co-benefits to livestock producers, while also preventing flood damage to local infrastructure.
• To expand water retention in the Canadian Prairies, the document recommends prioritizing wetland conservation, clarifying provincial approaches, evaluating cumulative storage needs, developing solutions that provide a bundle of benefits, and increasing funding for technical expertise in design and location selection.

APA

International Institute for Sustainable Development (n.d.). Natural Infrastructure Essentials: A focus on water retention. https://www.iisd.org/system/files/2026-01/natural-infrastructure-essentials-water-retention.pdf

Chicago

International Institute for Sustainable Development. Natural Infrastructure Essentials: A focus on water retention. n.d. https://www.iisd.org/system/files/2026-01/natural-infrastructure-essentials-water-retention.pdf.

Wikipedia

{{cite report |author=International Institute for Sustainable Development |title=Natural Infrastructure Essentials: A focus on water retention |url=https://www.iisd.org/system/files/2026-01/natural-infrastructure-essentials-water-retention.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{internationalinstituteforsustainabledevelopmentndnatural, author = {{International Institute for Sustainable Development}}, title = {{Natural Infrastructure Essentials: A focus on water retention}}, institution = {International Institute for Sustainable Development}, url = {https://www.iisd.org/system/files/2026-01/natural-infrastructure-essentials-water-retention.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }