Swale End Design Question

We are trying to install 6 swales, on contour, to partition a 165' by 165' plot of gentle grade into 5 paddock spaces, of more or less equal area. Given the relatively small size of this project and the short length of the swales, we are curious as to how best to design the ends of each swale to best utilize excess water that may not absorb into the paddock spaces and swale plantings. We have a relatively clay rich soil here in Central New York State (zone 5A). The plot is sometimes water logged during rainy season and the swales will serve to mitigate this as much as to prepare for dry spells. We were hoping to dig catchment pools at each end of each swale so that a pool defining the upper boarder of each paddock space might supply that paddock with a watering trough during wet seasons. I have attached a sketch of this concept.


We were also considering establishing Krater gardens of some sort as an alternative to catchment pools for watering troughs. Ideally we would like to utilize the run off water, which will likely be rich with bio-nutrients in some fashion. But have no experience with swales so far and would welcome any advice the community might have.

If you are planning to have ponds for animals to drink water at each end of the swales I suggest you dont.
Stock will ruin the pond and slowly fill it in.
Use troughs supplied by pipes and have some rocks in them for birds yo drink.
Here is a good site for you. https://www.tenthacrefarm.com/permaculture-swale/

From that site
The pink line are the contour lines.
Potential swale trenches are drawn in blue, while the planted berms below them are green.
Without swales, the water on this hillside would rush down and form gullies, taking precious topsoil and nutrients with it.

My strategy for swale overflow, is to only have one overflow per swale, and to have the overflows alternate ends in each successive swale.

Arranging for perfectly level matching spillways is really hard in practice. Small variations in instruments, and technique make huge differences in where the water actually flows. Animals trample spillways, causing them to change shape. Spillways collect debris and sediment. Easier to design from the beginning to have only one spillway. Having alternating spillways keeps the water fresher, and more oxygenated during runoff events.  

Thank you for the input so far! It is so helpful! We are starting this plot from scratch and want to do it right!

We are also wondering how best to determine swale depth?

The plot is South-East facing with an 8 to 12 degree slope and is around 30-40% clay. It receives significant run off from high ground to the North and West after heavy rains. The ground is often soggy in places.

Thank you!

It seems to me like the width of the swale matters more than its depth. Animals can really trample narrow bunds. Although, I often start by building short, narrow bunds, and then modify them after I see how the water is actually flowing. I'm using the crudest of surveying equipment -- A level on an A-frame, or on a string.

The top swale especially may collect a lot of sediment, and could benefit from added height. I typically use the collected sediment to increase the height and width of the swales. The bigger the swale to start with, the longer it will take to fill with sediment. I'm building swales with hand tools, so I like a little bit of continuous building over a long period of time.

I would not encourage the use of hand tools for what you are planning.
There is much written about construction techniques, if you cannot find something let us know?
Well built swales do not need silt, they maybe wide and need to have the volume to hold runoff water.
If you have too many, only the top one may fill.
What is your rainfall and how big is the paddock?