Unless we change the way we use water, we’re screwed.

According to a recent United Nations report, the world could suffer a 40 percent shortfall in water by 2030. To avoid that, we have to manage the precious resource better — and we have to do it now. A senior NASA scientist predicts that drought-stricken California has just one year of water left.

Sao Paulo, Brazil is in even worse shape. Experts say that South America’s largest city could dry up in the next six months.

In Sao Paulo, 40+ activist groups have joined forces to create the Alliance for Water. The group is coming up with policy changes to help the city cope with its water crisis. It’s also trying to build a new culture of water conservation.

To mark UN World Water Day on March 22, the group has published a Survival Guide to the Water Crisis for Brazilians. But a lot of these tips apply anywhere where water is in short supply.

No more singing in the shower

Your shower shouldn’t last as long as an Italian opera. And you know how it takes a second to get the water temperature right when you turn the shower on? Put a bucket in the tub to collect that water for use later. It’s even clean enough to wash your dishes with! When you’re ready to get in, you can put a wide basin in the tub to stand in that collects water as you bathe. This gray water can be used to water plants or for flushing your toilet. It’ll also help you limit your shower time: When the basin’s full, it’s time to get out!

2. Is your toothbrush glass half-empty or half-full?

Either way is fine — just don’t fill it up all the way. Half a glass is enough to rinse with after brushing your pearly whites. Dentists recommend using a pea-sized amount of toothpaste, which also makes rinsing easier. Keep a container inside the sink to collect the water you gargled with — you can always use it later!

3. Staying climate-conscious in the kitchen

Instead of washing your fruits and vegetables under the tap, clean them with a brush or towel. Then wipe them down with a cloth dipped in vinegar or lemon juice. Let them sit for an hour and give them a final wipe with a clean towel. Rice and beans for dinner? You can use less water for cooking by soaking them first. And when it comes to dirty dishes at the end of a meal, try using a piece of bread to mop up all of the extra sauce and leftover bits so the dishes will be easier to wash.

More dish washing advice: Fill a dish basin with 1.3 gallons of water and soap. Use it to wash your dishes. When you’re done, save the gray water to use for later. Fill the basin up again with clean water and use it to give your dishes a final rinse. This water is basically clean and can be used when you’re ready to do more dishes.

4. Revolutionize the way you do laundry

Do your laundry once a week, and do it in this order, recycling the water as you go. Wash your sheets first. Collect that water, and use it to wash your whites. Then collect that water to wash your colored clothes.

5. In case of prolonged water cuts, stop using your toilet

This might gross you out, but if there are prolonged water cuts, it’s best not to use your porcelain throne. You can collect your pee and discard it outside. As for poop, have you ever picked up after a dog or changed a baby’s diapers? In much the same way, you can wrap your feces in a newspaper, put the wad in a plastic bag and throw the whole mess out with your garbage.