Considering their watery origins, slugs and snails have adapted remarkably well to survival on land. When the air around it or the surface on which it is traveling becomes too dry, a snail can pull its entire body into its shell and seal the opening with a sheet of mucus, which then hardens, forming a secure closure. A snail can remain dormant in this condition for as long as four years. For much, if not most, of the growing season across the U.S., rainfall, fog, or morning dew will provide enough dampness to encourage slugs and snails, and during dry spells, most gardeners deliberately water their gardens to enable plants to grow. So, in most cases, eliminating moisture altogether is impossible.
Water management comes down to mitigating the effect of rainfall and watering.
If slugs and snails are a problem, and you are overhead watering, do so early in the day so plants have a chance to dry off before nightfall, when these pesky mollusks move about and feed. Where appropriate, use underground drip irrigation or leaky hoses that leave the soil surface dry. And build raised planting beds to ensure good drainage of upper soil levels. When setting out plants, leave adequate space between them so moving air can dry plant surfaces. Reduce the area blanketed by dense ground covers, or relocate dense plantings away from the vegetable patch.