Recently a swale was dug by a land-mate of mine using a rented bobcat. I made a type one error in that I neglected to survey and peg a level line. Instead I pegged parallel with a contour line that was about 5 feet downslope. This resulted in the swale having one end lower than the other. It is a slight grade but it is significant enough that after a rain, the only puddling that occurs is about 8 feet along the low end of the swale. The swale itself is about 60 feet long.
So my dilema is; what is the best way to fix this? My inkling is that I should raise up the lower end, to be level with the higher end but maybe I've got that wrong. Maybe I should match the high and low ends to the middle?
Some further info:
-The swale is along the edge of a laneway so it can't really be adjusted uphill
-the soil is sandy, so digging (if necessary) will be relatively easy
-I have lots of sod in a massive pile that is about 70 feet from the farthest (and lowest) end of the swale. So I'm thinking of just dumping sod on the lower end to level it with the higher end.
when i am doing terracing here, and i end up with terraces slightly off. if i have extra dirt i add it to the lower end to match. if there is no extra soil, i find its best to take from the high end and pull it lower to match, you might have to make the swale longer to get the extra soil you need, but shouldn't if you do it carefully.
The ultimate goal of farming is not the growing of crops, but the cultivation and perfection of human beings. - Masanobu Fukuoka
I was thinking about taking from the high end to add to the low end. I guess I'd just have to be careful not to take so much that I make it a lower elevation than the downside of the high end of the swale.
As a temporary measure (and also because I needed a path across the swale) I ended up putting a clay land bridge about 10 feet in from the highest edge of the swale. It's almost level between the high end and the bridge, and starts sloping more dramatically on the lower side of the bridge. I know that most of the water will percolate through the ground below it but at least it'll keep any standing water from flowing downslope on the surface.
You can put stones in the swale to slow up the waters movement down hill, like making small dams in streams, some swales are made like this with stones in to slow down flow I have seen photos of them in internet. I think swales are just drainage courses, canals in a small way made by people who want to direct water on their land rather than great canals watercourses that cross a country. THey are canals whose floors have not been waterproffed so they do take up water but not too quickly. That you use them to hold water and allow see pn rather than run off instead of to direct water to where you want it to go or away from something you don't want to get wet, is your affair and a permaculture irrigation in depth affair. As the swales are meant to have plants in the bottom of them to sure them up, grasses for example, as are any cuttings in hills made for roads meant to be planted up to stop erosion of the cutting. All easily eroded plaeces should be p'lanted up to stop erosion. Swales are only meant to hold or carry water after it rains not all the time, so grass should be able to grow in them. The plants should stop the water running down the swale if the incline is very small.
Darrel Doherty puts slight downward incline into his swales. If you imagine the line of hills as being scallooped so that if you walked along the bottom of the hills you would be walking in S shaped lines walking round promontries and inlets, well, as the inlets get wetter than the promontories because the slopes face into them as well as downwards not outward towards the most salient bits of the hill. water drains away from the crests of the hills, so daren doherty puts in swales that keep the salaent bits of the hills as wet as wet as the rest of the hill with a slight incline todown towards the most salient parts of the hill . He says the water only runs down the slight incline of the swale in a specialy heavy water event. So maybe you don't have to worry about the slight incline in normal circumstances.
Darren Doherties idea must be good for keeping the whole slope irrigated but not so good for water harvestring if part of you interest in water harvesting is filling underground water which happens better if there are pockets of water, puddles where the water seeps in and key points where it collects and seeps in to the ground. If you lead it out to the points that dry mostl easily it will return to the air, evaporate. If its equally distributed then there wont' be so much water just hanging around in key ppints till it sinks in. The water will be more likely to evaporate off the land spread thin. Thats why irrigation is a doubtfull thing, it is better to grow a drier country crop on dry land than to irrigate. Irrigation does not sink into the ground very deeply and evaporates easily. I have drip irrigation so I do use it am myself am guilty of using it. Farmers however work on a bigger scales than gardeners and if they grow maize instead of wheat here in Spain were summers are dry and maize does not ripen untill late in the year unlike wheat that ripen before the dry season startd, then the farmers are going to use enormouse quantities of water, they are the group who uses most water if i remember right so they need whatching. It should not be have a shower and not a bath it should be, what are the farmers growing, rice in the deserrt?
You can turn the swale into steps instead of leaving it as a ramp. If the horizontal part of the steps inclines slightly, is slightly lower on the up hill side than the down hill side of the step then the water will collect in the back of the step and sink into the ground at regular intervals. Just having a bumpy bottomed swale with hollows in it should work, puddling helps water get soaked into the earth instead of running off it . The uneven surface should do the same as backwardly inclined steps would do, it would be to have pools of water that sink into the ground instead of running down the swales. agri rose macaskie.
I ended up levelling th swale across the whole length. It rained today and it was nice to see an even distribution of water in the ditch (aside from about 3 feet at the end where I didn't finish before the thunderstorm)
I used the middle portion of the ditch as my model elevation because it was the area with the longest level section. I used soil from the high end of the swale to fill in the low end. I also had some sod left over which I placed at the low end of the swale's upper edge ( the contour line at the high elevation side of the ditch)
Just visualise stepping stones crossing the swale without spaces between them. i can't remember where i saw the picture of the grassy swale with stones in it. I dont mean stones all along the bed just every so often to break the flow of the water down to the lowest point. I have a sloping path that takes us down the slope and i thought i could put steps in it that sloped backwards so the water in each step was thrown to the back of the step and not down towards the step below it were it might overflow on to the step below it and so down the path. agri rose macaskie.
I put a series of short berms that run perpendicular to the swale every 10-15 feet or so ... as mentioned above, these also act as bridges (for foot traffic and wheel barrows).. With this system, no need to worry about surveying, it prevents all the water from going to one side and topping over the lowest part.
i have drawn some pictures but i think i will put them in a new thread where all the drawing i have on the topic can be found easily. I have made drawings on key hole spots is that the right m¡name it is gettign very late to be writting and saddles in the hills were you can put in a pond and such and if its all together but more than that under a heading that indicates that the thread has lots of information on just that i think it will be more usefull. I hav e just messed up trying to send a photo and got on the post bit somthing else nd not been able to take it down. rose macaskie.