HEMP HELPS PREVENT FLOODS

Editor's Note: There is some serious innovation happening out Taber way that could help us mitigate the effects of flooding. It's fast, cheap and effective. Sound too good to be true? It's not, and it could help YOUR region deliver cleaner water from the fields back to the river too. After all, you care about what is used to grow your food, right? Many thanks to Taber Irrigation District's Christopher Gallagher for this guest blog post!

Taber Irrigation District SAWC Project #3 – Lateral 18 Taber Water Quality Improvements

The irrigated parcels of land in this area - SE of Taber reservoir - used to be watered via an open canal. They are now delivered by a buried pipeline. This means there is no seepage or evaporation losses - and farmers have more pressure at their pump sites. The farmers have to pump the water from the point they receive it, in order to run their on-farm irrigation systems. Deliveries of irrigation water for the Lateral 18 system have thus had a radical makeover! 

Now farmers can operate more efficiently, with cleaner water. Normally, with an old canal system, it would be simply back-filled. In this case, and in other recent cases, TID has been leaving the old canal in place in order to receive field drainage (extra rain water and everything that comes with it).

 TID Infiltration Weir: Rubber Liner and Infiltration Chambers – Looking Upstream

TID Infiltration Weir: Rubber Liner and Infiltration Chambers – Looking Upstream

What this project does, by leaving the old canal in place, is maximize the benefit of that system to clean up the storm water and field drainage before it gets to Taber Reservoir. The water from the reservoir is the mid-point of the entire TID irrigation system - and is used by other farmers further down in the system. (Remember we are always saying "We Are All Downstream"?)

Fourteen (14) structures (Editor: 4 different types designed by engineer Christopher Gallagher) slow water down so that sediment, and the pollutants sediment carries, can settle out. The sediment also provides a good base for plants, like cattails. These are excellent filters of nutrients and other things in the water we want cleaned up - like bacteria and pesticides. They are like the kidneys of the wetland. Also, the systems provide good, wet conditions for this type of beneficial plant to establish.

 TID Permeable Check (8X) – Check boards with Spacers

TID Permeable Check (8X) – Check boards with Spacers

These new structures have been installed in the last 4km of the old canal leading to Taber Lake Reservoir to detain and treat storm water and field drainage. These included 8 permeable checks, 2 permeable weirs, 2 infiltration checks and 2 infiltration weirs. So all structures will reduce upstream bed scour, encourage settlement of fine sediments and enhance establishment of this beneficial vegetation.

They will also absorb incoming flood events, attenuating the flow over a much longer release period. So if we get a major rain event and water comes down from upstream, these structures allow the water level to rise throughout the entire canal and slowly release it over several days, after the storm is done. That helps us better manage water. No one wants polluted storm water dumped in the river.

 TID Infiltration Check: Completed – Looking Upstream

TID Infiltration Check: Completed – Looking Upstream

Infiltration structures have the additional, unique feature of a hemp straw core. So why hemp? We needed a high-carbon, organic source for the soil bacteria to grow on. Hemp is a very woody plant and has good durability - it will last a lot longer than wheat or flax straw. Hemp straw is readily available since farmers in Taber are harvesting hemp oil - so it's easier to obtain than wood chips.

 TID Infiltration Weir: Installing Hemp Straw – Looking Downstream

TID Infiltration Weir: Installing Hemp Straw – Looking Downstream

The hemp acts as both a physical filter to capture and absorb bacteria and pesticides, and is a high carbon medium to colonize denitrifying soil microorganisms. Recent testing on a hemp straw tile drain filter in TID shows a significant beneficial effect. This is a larger scale pilot project on an open drainage channel to see if these ideas merit use in other similar systems.

 TID Infiltration Check: Dual Infiltration Chambers with Hemp Straw Carbon Medium on Rubber Liner – Looking Downstream

TID Infiltration Check: Dual Infiltration Chambers with Hemp Straw Carbon Medium on Rubber Liner – Looking Downstream

Editor: Is this project being done anywhere else? Nope - it's completely innovative for Southern Alberta - led by Taber Irrigation District. But these are also opportunities that could benefit us all in the Oldman watershed by helping improve the quality of water from all counties and MDs to the river. It's also relatively inexpensive and easy to install, so many thanks to Chris Gallagher and his team at TID for the project, the blog posts - and for being an outstanding contributor to the Southern Alberta Water Charter!

Chris will be in attendance for the closing ceremony of the #SAWC17 at the Southern Alberta Ethnic Association on November 17th at 10:00. The event is free, and everyone is welcome to attend and speak to all 42 signatories about their projects directly - but please register at: 

https://www.eventbrite.ca/e/sawc17-closing-ceremony-tickets-38092511728

 

 TID Permeable Weir (2X) – Infiltration Chamber within Rock Weir

TID Permeable Weir (2X) – Infiltration Chamber within Rock Weir

 TID Infiltration Weir: Completed Windrow Looking Downstream

TID Infiltration Weir: Completed Windrow Looking Downstream