Headwater Streams and Watersheds

Headwaters

• Headwaters are the foundation of our watersheds and include small streams, vernal pools, off-line ponds, parts of the groundwater system, and wetlands.

Small Streams and Their Drainage Areas

• A 1st order stream has no tributaries and can occur anywhere, flowing into the ocean, lake, wetland, or any part of a river.
• A 2nd order stream forms where two 1st order streams meet.
• Stream order is not affected when a smaller order stream joins a larger stream.
• Headwaters can be either ephemeral (flow based on precipitation or meltwater) or intermittent (flow occurs when the water table rises).
• Higher stream orders drain increasingly large areas.

Vernal Pools

• Vernal pools are temporary features forming mostly due to precipitation, providing important spring habitat for amphibians and waterfowl.
• Vernal pools both evaporate and drain into local groundwater.

Off-Line Ponds

• Off-line ponds are normally spring-fed and do not have surface connections to other local waters.
• An off-line pond differs from an on-line pond, which occurs along a stream.

Groundwater

• Portions of the groundwater system that are part of headwaters include groundwater recharge areas, shallow aquifers and wells, and areas of groundwater discharge or up-welling.
• Ontario has a high degree of interaction between ground and surface waters due to the geology of the Oak Ridges Moraine and the Niagara Escarpment.

Wetlands

• There are four types of wetlands: marshes (open water and plants like water lilies and cattails), swamps (wet areas dominated by trees and shrubs), fens (ground-fed areas high in dissolved minerals and dominated by sedges, grasses, and reeds), and bogs (peat-filled areas with acidic and low-nutrient water and little plant diversity).

Importance of Headwaters

• Headwater streams form the majority of the total length of all streams in any watershed.
• Headwater drainage areas (catchments) drain the majority of a watershed's area.
• Headwaters influence water quantity in two key and complementary ways: they provide the bulk of flow to water courses and regulate that flow through natural cover, soil type, and geology.
• Headwaters impact local soil moisture and plant types, infiltration to groundwater, and the speed and volume of runoff, which influences downstream erosion and flooding.
• Headwaters pick up, blend, and deposit significant portions of a stream's nutrients, organic matter, and sediment, thus defining water quality downstream.
• Headwaters nurture the largest portion of a watershed's biodiversity, providing key habitats for numerous species.
• About 33% of all Canadian species require wetlands at some point in their lives.
• Most larger species downstream depend on smaller species upstream.
• Terrestrial insects are as important a part of the food chain as are aquatic insects.