{"id":210,"date":"2025-03-13T03:54:47","date_gmt":"2025-03-13T03:54:47","guid":{"rendered":"https:\/\/wordpress.evergreen.edu\/bittersweet-abroad-w25-baker\/?p=210"},"modified":"2025-03-18T17:17:26","modified_gmt":"2025-03-18T17:17:26","slug":"bonus-post-ii-prep-work-for-the-water-catchment","status":"publish","type":"post","link":"https:\/\/wordpress.evergreen.edu\/bittersweet-abroad-w25-baker\/bonus-post-ii-prep-work-for-the-water-catchment\/","title":{"rendered":"Amateur Hydro-Engineering for Fun and Profit (no profits were made)"},"content":{"rendered":"\n

I would like a weir.<\/p>Nicola Shirley-Phillips of The Source Farm via WhatsApp prior to our departure for Jamaica <\/cite><\/blockquote>\n\n\n\n

During the chaotic lead up to our study abroad pivot from Trinidad to Jamaica, I had the good fortune to reach out and attempt to lay some groundwork before the travel was even approved. Through pure providence, I have an extended family connection to The Source Farm Ecovillage<\/a>, specifically Nicola Shirley-Phillips, Colleen Williams, and Nomi and Dwight Shirley. Not about to let a perfect one-for-one replacement site slip by a number of WhatsApp conversations led to an eventual link up while on ground!<\/p>\n\n\n\n

During the conversations, the lack of water access for the Guango Wild Garden Conservancy (GWG)<\/a> was brought up. Without water, the processing center at the site was unusable, and by extension the Source’s activities with the Ujima Organic Market suffered. This seemed like the perfect<\/em> place to apply some nondestructive learning in the form of labor support to the effort.<\/p>\n\n\n\n

Conversations lead to the understanding that emplacing a weir. Awesome. Now wtf is a weir?! Put simply, a weir is a kind of restricted flow barrier placed in a channel. It holds water upstream in a weir pool, and allows a flow-through, or crest, that can manage the holding pool height, weight\/pressure of water upstream, and down stream flow all from a single point. As cool as it sounds, there is a lot of variation to weir design and it can have major impacts on its effectiveness, longevity, and usefulness.<\/p>\n\n\n\n

I’m a hands on learner, so armed with all of humanity’s collective knowledge<\/a>, I grabbed some scrap aromatic cedar off-cuts, a handsaw, my dog, and some plucky determination before setting off for a backyard creek to test different weirs.<\/p>\n\n\n\n

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As good a spot to weir as any, right?<\/figcaption><\/figure><\/div>\n\n\n\n
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Test site cleaned and modified to test weir plates.<\/figcaption><\/figure><\/div>\n\n\n\n

The opening of a weir is called an orifice. It determines the flow-through capabilities of the weir, as well as its water retention capacities in the weir pool. Trial an error was the name of the game. 20\u00b0 V notch weir? Too small. 90\u00b0 V notch weir? Too big. 4″ Rectangular Weir? Too basic. 4″ Rectangle-to-45\u00b0 Compound weir? Too complicated. It seemed my stock of cedar was destined for a waterlogged graveyard of failure.<\/p>\n\n\n\n

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Compilation of failed designs. The dashed line shows the 60\u00b0 trap weir orifice. Foreshadowing…<\/figcaption><\/figure>\n\n\n\n

Before giving up and going back to being Curt in the Dirt with no water creds, I tried a trapezoidal weir. A V notch whose bottom is a simple flat edge. Perfection. The V allowed for increasing outflow as the water backed up, while the half-rectangular bottom allowed for consistency. Eureka!<\/p>\n\n\n\n

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Top-down view of the weir plate (and scraped failures). Not the weir pool height (bottom) compared to downstream flow (top). That’s a lot of water retention!<\/figcaption><\/figure><\/div>\n\n\n\n
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9 out of 10 engineers recommend Crest.<\/figcaption><\/figure>\n\n\n\n

I left the weir in place for 15 minutes to track pool growth and retention. I observed my spillway (made of a piled stone “leaky” weir) offload the overflow of the weir pond. I measured the crest and reinforce the downstream flow with flat stones to prevent scouring (washing away\/removal of the stream bed due to crest flow). All was working. The lessons learned in observing failure made the observations of success sweet indeed!<\/p>\n\n\n\n

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Centered in the channel, anti-scoure stones at the crest, clean flow-though, a calm\/straight weir pool above, & a leaky weir serving as the overflow spillway (right side of image). That’s a damn fine weir.<\/figcaption><\/figure><\/div>\n\n\n\n