I agree with Philip and would add, you will, on average, need less water than Spain and France. I never concern myself about water issues going up the coast. Have two bottles (1.5l max 2l) and you will be fine. Churches, gas stations, supermarkets, public toilets, etc, are scattered all along the route. You’ll also have fast-flowing streams in the remote areas to keep you topped up. Don’t fill up from streams in farm areas as there may be pesticide runoff from the crops.