Rainwater can be harvested from your roof, non-toilet water can be used in landscape or garden, and topography on your land can be altered to spread and sink water.  In Massachusetts we have metal roofs without gutters and for now place buckets, trash cans and the like and syphon the water to the gardens which are lower than the house.  Be sure to use the water to empty each open receptical frequently during mosquito season.  In CA we used large closed tanks as there the strategy was to use a large amount of rainwater over a few months in the latter part of the dry season when springs and ponds get slower and lower.  Rainwater with its ions and lower pH is better for plants than even well or spring water, and certainly much better than chlorinated municipal water.  It is worth the effort, AND the slow flow of gravity fed water means I can tend and weed and observe the areas being watered.   If using drip irrigation the rainwater actually removes some mineral deposits from groundwater used at other times in the dripper lines.  Even an asphalt shingle roof has little contaminants that will harm plants (allow the first few rains to wash off a new roof, or if in a polluted urban area when it hasn’t rained recently).  As dry spells get longer even in rainy summer areas, rainwater storage quantitles may need to be increased.