Instead of boiling vegetables, steam them; it takes a fraction of the water and helps retain more nutrients, too.
Squeeze more out of your cooking water by cutting the amount used to boil pasta or potatoes; just enough to submerge those starchy staples is enough. Pasta and potatoes can be cooked in the microwave with less water than conventional boiling, too.
Make your cooking water do double duty. Steam the vegetables with rice, potatoes or pasta; just put the veggie steamer right on top as the starch cooks below. The rising steam in the covered pot will cook both with the same moisture. Besides saving water (and cooking fuel), you’ll have fewer pots to clean, too.