If it continues to not rain, we'll run into a water shortage.
"もしこのままずっと雨が降らなかったら水不足にる、"
If it never rains ですか？「このままずっと」
->If it continues to not rain, we'll run into a water shortage.
->If we continue to not get any rain, we won't have enough water.
他：
- We may run out of water if we don't get any rain sometime soon.
- We're going to have a water shortage if it doesn't rain.
If we continue to go without rain like we have been, there will be a water shortage.
If this dry weather continues like it has, there won't be enough water for us.
この場合、次のような言い方ができますよ。
ーIf we continue to go without rain like we have been, there will be a water shortage.
「もしこのままずっと雨が降らなかったら、水不足になるだろう」
If we continue to go without rain like we have been, ... という言い方ができます。
ーIf this dry weather continues like it has, there won't be enough water for us.
「このように乾燥した天気が続いたら、水不足になるだろう」
If this dry weather continues like it has, ... という言い方もできますよ。
ご参考まで！
アメリカ合衆国 
カナダ 
