Water and Heat
Dehydration can kill us. For cyclists this can happen through clouded judgement causing a fall or collision well before the actual water shortage does us in. At lesser severity, getting dehydrated is really unpleasant, and can knock the wind out of us for many hours. I've been well served by an old bushwalking rule: never go past a water source without filling up your containers.
Is the water potable? There is a growing lack of taps at service stations, and increasingly, the water is not treated. At any of the smaller river towns, I always check if the water is treated, or straight out of the river.
How much water do we need? The crude but effective method is to look at urine production: "If it's clear, never fear. If it's straw, drink some more." How long since the last toilet stop?
Another metric that I think has some merit is that if we suddenly find we are draining more than half a 750 mil bidon, we are not drinking often enough.
For 30 degree weather (and up) I allow half a bidon per 20 minutes. With four bidons on the bike, that gives me a two and a half to three hour range. My long-term good average speed is about 18kph (real time, not road speed) so following a decent drink on leaving a place, I expect to cover 80km comfortably, and maybe squeeze another half hour after that without too much discomfort. (Assuming I am not already carrying a water deficit.)
Sounds conservative? It is; you don't mess with this stuff. It doesn't matter if we arrive with two full bidons; it matters a hell of a lot if we run out of water. This stuff sets in fast: back in the seventies, people stopped on the Hay Plain, and asked if I needed water. Like a fool, I said I was fine— I was. An hour later I was really sick, and there were no more cars.
A slight rise in temperature can drastically increase water use. Warm head winds increase water use. The increase is more exponential than geometric. For example: "From Bordertown to Keith is 56 kilometres. I rode this in constant rain Tuesday January 12, drinking only a litre of water. On the previous day, for the 38 kilometres between Tintinara and Keith, in 45 degree midday heat, I drank five litres of fluid."
Judgement is essential here. Last year, I took refuge in shade at Wilmington around 1pm because it was too hot to travel. An hour or so later a young bloke came past— with bob-trailer, too— heading south, and quite comfortable. The difference was that he had the wind behind him, and he had cool water buried in the middle of the trailer. My bidons were on the frame, and drinking hot water would add to my body heat and make me sick. My next stop was Quorn, which was 40 kilometres away, with no water stops.
I've travelled extra hot days— forecast maximum of 45 degrees— by having frozen water bottles in my panniers, and buying cold 1.5 litre replacements. But you can only go so far on this; powered tent sites don't come with a refrigerator, and even bottles insulated by a pannier still warm up. In this kind of weather, the bottles marketed with insulation are a waste of time if you have them exposed on the bidon clips. I've usually ended up stopping by 12 or 1pm, and sitting out the heat of the afternoon.
We simply have to allow the amount of water we can carry to dictate our range and expectations. Stopping for four or five hours in the middle of the day can help, although it takes a long time to cool down. Starting before dawn, if the road is safe, is another strategy. You can get seven hours in by midday.
Planning to camp on a long stretch? Have you factored in a couple of extra litres for water deficit that has built up during the day, as well as overnight water, and the water you need to get from the camp site to the next water source?
Sports drinks are marketed as having salts to enable recovery and prevent Hyponatremia. My experience is that if I am eating pies and steak sandwiches, there is enough salt in my system. At my level of exercise, PowerAde and the like mostly seem an expensive way to buy sugar. (eg: here and here.) It is the water that counts.
The extra bidons on the down tube are held on with heavy cable ties. I've added a couple of extra ties around the gear cable housing stops to stop slippage down the tube. The bottom bidon was for a desert trip. The water gets tainted by the plastic when it's really hot. Normally, I use this holder for a few small tools and chain oil, but they need wrapping or they make a racket, and can also shake apart. I once had to rebuild a multi-tool before I could use it!
I found I needed a smaller bottle so as not to foul the front tyre. If you buy an oversize bottle cage to take 1.5 litre drink bottles, make sure you have the bike with you, or that they will take the product back; my frame didn't have enough room for the bottle to fit in on the seat tube.