RECOMENDACIONES PARA FUTURAS INVESTIGACIONES

The Broughton’s Creek is a tributary of the Little Saskatchewan River and is located in

southwestern Manitoba, Canada (Figure 3-1a). It drains an area of approximately 252 km2 (Figure 3-1b). The Broughton’s Creek Watershed (BCW) can be described as a typical PPR landscape which was created between 20,000 to 12,000 B.C due to the retreat of the Assiniboine glacial lobe (Wang et al., 2010; Yang et al., 2010). This area has numerous potholes, sloughs, and lakes and is described as a hummocky till plain. Most soils in the watershed are well-drained Newdale association soils (i.e., mainly Orthic Black Chernozems). However, some near-stream locations also have soils from the Dorset, Drokan, Eroded Slope Complex and Jaymar associations (MAFRI, 2008; Wang et al., 2010). According to the U.S. soil taxonomic classification, the Udic Boroll subgroups have similar properties as soils from the Newdale, Dorset, and Jaymar associations (Soil classification working group, 1998). Most of the land in the BCW is used for agricultural purposes (71.4%), followed by rangeland (10.8%), wetland (9.8%), forest (4%) and other uses (4%). Detailed landscape change detection studies have shown that between 1968 and 2005 approximately 21% of the wetland area in the watershed has been lost (i.e., those are, currently, fully drained wetlands that no longer have an open water component). However, 70% of the wetland area has been impacted when we account for all hydrological alterations, including partly drained wetlands and farmed wetlands (Wang et al., 2010).

For continuous monitoring of wetland hydrology, thirteen open water PWs and seven drainage ditches were selected on both sides of a 5 km creek reach in the BCW (see Figure 3-1c for the exact locations). Out of the thirteen open water PWs, ten are intact PWs (i.e., hydrologically undisturbed wetlands) and the remaining three are consolidated PWs. According to Ducks

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Figure 3-1: (a) Location of the Broughton’s creek watershed within Canada. (b) Creek reach and surrounding land under study. (c) Instrumented wetlands in the Broughton’s creek watershed.

I: Intact wetland, C: Consolidated wetland, D: Drained wetland(s) and associated ditch(es). The black cross shows the creek water level measuring location. (d) Example of consolidated wetland, C2; dashed circles indicate historic wetlands that have been drained into C2.

Unlimited Canada’s (DUC) wetland inventory established for the BCW, there were no

morphological changes to the intact PWs in the last 60 years. However, multiple PWs were drained to form a consolidated PW (see example in Figure 3-1d). Drainage ditches have visible surface

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connections to the creek reach and are typically located downslope of fully drained PWs. Drainage ditches were selected based on the same previously mentioned wetland inventory dataset, which includes the location of historic PWs and confirms their role in diverting water from the drained PW basins to the creek reach. As indicated by Haque et al. (2018), over time these ditches have accumulated a lot of eroded materials, and overland flow through them is rare except during heavy rainfall.

A series of wetland spatial characteristics (Table 3-1) were calculated for all studied PWs (i.e., open water and fully drained) using the wetland inventory dataset provided by DUC. For open water PWs, DUC used the V-A-H method (Pomeroy et al., 2010) to calculate storage volume since this method can estimate volume below the standing water from LiDAR data. However, for drained PWs, the Surface Volume Tool in ESRI ArcGIS was used to calculate volume from LiDAR data. The areas of the open water PWs range from 7.4×10² to 1.5×10⁵ m2_{, while their}

storage volumes range from 7.4×10¹ to 4.4×104 _m3_{. The drained wetlands associated with the} instrumented ditches had areas and storage volumes ranging from 7.8×10² to 1.3×10⁴ m2 _and

1.5×10² to 7.0×10³ m3, respectively. Euclidean distances estimated between each open water PW and the study creek reach range from 4.7×10² to 1.0×10³ m, whereas ditch lengths for the drained wetlands range from 9.3×10¹-2.2×10² m. Catchment areas for the open water and drained PWs range from 6.0×10³-3.1×10⁵ m2 _{and 9.8×10³-9.0×10⁴ m}2_{, respectively. Some spatial characteristics} such as the incremental contributing area (ConArea) and the total drainage area (TotDrainArea) are only relevant for the consolidated open water PWs and drained PWs. The incremental contributing area of a consolidated PW was calculated by summing up the catchment areas of all the drained PWs that pre-existed the consolidated PW.

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Table 3-1: Overview of wetland spatial characteristics for open water (i.e., current) and drained (i.e., historic) prairie pothole wetlands. I: intact wetlands; C: consolidated wetlands; D: drained wetlands.

Name Abbreviation Valid for Description (units) Range

Area Area I & C

D Surface area of current or historic wetland (m²)

7.4×10²-1.5×10⁵ 7.8×10²-1.3×10⁴

Perimeter Peri I & C

D Edge length of current or historic wetland (m)

1.0×10²-2.8×10³ 1.0×10²-6.6×10²

Storage volume Vol I & C

D Storage volume of current or historic wetland (m³)

7.4×10¹-4.4×10⁴ 1.5×10²-7.0×10³

Bottom elevation Elev I & C

D Elevation of wetland or ditch bottom above sea level (m)

5.2×10²-5.3×10² 5.2×10²-5.3×10²

Spill level SL I & C Height of water (relative to stilling well bottom) at which wetland will spill (m) 6.1×10⁻¹-1.2×10⁰

Catchment area CatArea I & C

D Natural basin area (or drainage area) of current or historic wetland (m²)

6.0×10³-3.1×10⁵ 9.8×10³-9.0×10⁴

Catchment to wetland ratio Cat2Area I & C

D Ratio of catchment area to surface area for current or historic wetland (-)

1.8×10⁰-4.2×10¹ 3.6×10⁰-1.3×10¹

Catchment to volume ratio Cat2Vol I & C

D Ratio of catchment area to storage volume for current or historic wetland (m⁻¹)

6.2×10⁰-5.6×10² 6.8×10⁰-6.7×10¹

Catchment perimeter CatPeri I & C

D Edge length of current or historic wetland catchment (m)

4.1×10¹-4.8×10³ 6.6×10²-2.1×10³

Shortest distance to creek Distance I & C Euclidean distance between wetland center and nearby creek (m) 4.7×10²-1.0×10³

Ditch length Length D Length of drainage ditch routing water from historic wetland to nearby creek (m) 9.3×10¹-2.2×10²

Incremental contributing

area ConArea

C D

Increase in current or historic wetland catchment area due to human alteration, i.e., drainage (m²) 0.0×10⁰-1.2×10⁵ 0.0×10⁰-6.2×10⁴ Incremental contributing perimeter ConPeri C

D Edge length of current or historic wetland incremental contributing area (m)

0.0×10⁰-2.4×10³ 0.0×10⁰-1.8×10³

Total drainage area TotDrainArea I & C

D

Sum of wetland catchment area and wetland incremental contributing area for current or historic wetland (m²)

6.0×10³-3.8×10⁵ 9.8×10³-1.2×10⁵ Total drainage area to

catchment area ratio

TotDrain2Cat Area

I & C D

Ratio of wetland total drainage area to wetland catchment area for current or historic wetland (-)

1.0×10⁰-1.5×10⁰ 1.0×10⁰-2.3×10⁰

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Similarly, the TotDrainArea of a consolidated PWs was estimated as the sum of its original catchment area and its incremental contributing area.