They are on-contour “ditches” designed to “slow it, sink it, spread it” water that normally runs off a sloped property. Skillful surveying, staking and excavation of these can create a “water wiggle way” moving water from high energy, low potential upper elevations to low energy, high potential low lands slowly to increase the amount of time that the “edges” have to mingle and interact. Edges are where there is rich profundity and diversity as the “pressure” from one microclimate presses into an other. So where a water way passes through a normally more dry land, the water soakage and unique species that can thrive can be observed and cultivated.
Swales can slowly and passively distribute water over large areas or divert water from an abundant, wet area to a dryer area. A clever design includes use of ponds witch may have spill ways tat a swale lower in the property profile pick up or perhaps the swale is used to expand the catchment area used to harvest water to feed a pond.
Swales can be combined with Gabion dams (a form of “check dam”) which are purposefully leaky structures, often build of rocks or even haybales placed in streams. The leaky Gabions simply slow down what would be an erosive water way while allowing some of the water to pass through but also feeding the swale system, thus spreading that water. These are great ways to decrease wetness in marshy areas while also extending the water holding ability of the surrounding lands. The sild and soil buildup upstream from the Gabions will eventually become rich fertile areas where new crops orsemi aquatic plants can be cultivated.