What I learned this week at work is that how much water I drink during the day greatly affects how much milk I get from the breast pump. I did not expect a striking change, but now I've learned that lesson! Monday, I was "too busy" to refill my water cup, and didn't drink as much as usual; I pumped 2 to 3 ounces less than I expected. Tuesday I drank a normal amount, and pumped a normal amount. Thursday I decided to see if I could increase production by drinking as much water as I could remember to keep drinking, and I got 3 or 4 ounces more than I expected. I'd hazard a wild guess that every 12 to 16 ounces of water in excess of my usual water drinking yields another 1 ounce of breast milk.
Years ago, when I learned that drinking plenty of water reduced the number of afternoon headaches I got, I started drinking even more water. I don't know how this would work for mothers who are not heavy water drinkers, but I think drinking lots of water is a good habit for all working mothers!