Being that you are talking about a normally wet area, that is extra dry, it is a bit harder. Because for me where it is ALWAYS dry, I just do certain things, as a matter of course. For instance, Im looking to grow much of my grains in the winter, when water is more regular.....
you have a long growing season, even if it continues to get drier, Im betting with the right crops, you can readily find a long enough time period that is wet in which to grow..... I need more details of your plans, intentions etc.....
anyway, the basic stuff, is mulch. actually this serves many purposes. Many say this attracts pests, and gives them a place to live, but Ive seen others in the same areas, saying that isnt an issue for them. certainly hasnt been an issue for me, but somehing to be aware of. Use pebbles if thats true for you. Or even fist sized rocks.
the SUNLIGHT, more then the heat cause evaporation. keep that in mind as well.
But knowing nothing of your conditions, or intentions, about all I could say is a good mulch layer, whether it is straw, leaves, pebbles fist sized rocks, plastic(although the soil likes to breath, plastic isnt the best)