I drink about 1.5 liters a day. That seems quite small to me. When I drink about 1.5 liters a day, I have a dark yellow one too. It hasn't happened to me since I drank around 3 liters / day. The doctor once told me. One should drink so much fluids a day that the urine is colorless. PS: And then it happens that it's very yellow when someone takes a B-complex, for example.