Terraces into swales?

A few acres of my place have terraces that have been in place since at least the late 1950's. They need to be rebuilt to divert the water off the field as they have washouts and are holding water in places. The soil is TX Blackland prairie, a.k.a. clay. As I'm not interested in using land as one large field, would it be advisable to convert the terraces to swales? The land area that is terraces is about 12-15 acres and is abandoned cotton land that has been grazed off and on since the 60's. Mix of grasses and cedar, honey locust, and brambles. I've mowed most of it just to get a feel for the lay of the land. But I would like to either build a pond or swales for water. Being TX, I get an average of 50 inches of rain a year, but which year that was I don't know! Actually, the year we bought this place, there was 100 inches. And last year, well, I grew up in the desert of NM and I've never seen it as dry in NM as it was here.
So what I'd like advice on, is on this soil type and rain potential, should I continue to divert the water off the field or put swales in and go full bore permacutlure on this ground (my preference). I' need to decide something soon so I can get my equipment in to work the soil before this fall and the rains start. The ground is slicker-than-snot when wet. If I get a chance, I'll attempt to post pics of the ground.

Personally I would not divert water off the field, but put in quite large swales for the large amount of rain you might expect. Look at Geoff Lawton's swales in the subtropics, they are enormous and fill with a lot of water.

You can see some in this video: http://permaculture.org.au/2012/06/01/zaytuna-farm-video-tour-apr-may-2012-ten-years-of-revolutionary-design/#more-7542

You can go with drought tolerant species like jujube, mulberry, spineless prickly pear and use mesquite for n-fixer.

I would suggest caution in regards to planting mesquite.
True, it will fix nitrogen, and survive almost any drought...a single tree has been known to have a tap root over 190' deep (58 M), and surface roots to cover nearly an acre (0.4 ha).

However, if planted too thickly, they can actually lower your water table (permanently)!

Here's a video about combining swales with a pond: http://www.youtube.com/watch?v=E79C9tdcgEA&feature=related

This is the one I was looking for: http://permaculture.org.au/2010/12/15/a-guide-to-back-flood-swales/

John Polk wrote:I would suggest caution in regards to planting mesquite.
True, it will fix nitrogen, and survive almost any drought...a single tree has been known to have a tap root over 190' deep (58 M), and surface roots to cover nearly an acre (0.4 ha).

However, if planted too thickly, they can actually lower your water table (permanently)!

John can you expand on the whole mesquite lowering your water table thing... Does the long tap root funnel shallow water tables deeper or what?

I don't believe that the mesquites will funnel the water deeper. What happens is that they will consume water if it is available to them. If they are planted thickly, they have the capacity of consuming more water than falls from the sky. If this continues for several years, your water table will lower.

Though they are amongst the drought hardiest trees alive, if water is available, they will consume it in huge quantities so that they may store it for future use. If there are too many of them, they will leave little to nothing for the other plants in the vicinity. Imagine a tree whose survival mechanism is to send out an acres worth of roots. Now, set a couple hundred of those on a single acre and see what else they allow to live.

Howsomever, here in Texas, you don't have to plant mesquite, just wait and soon your land will be covered. I don't worry about it, the horses, goats, rabbits, etc. all seem to find it yummy. And it does provide a certain amount of shade.

Certainly works great for BBQ's. That authentic SW flavor.