More than 60 per cent of an adult's body weight is water. In children, this proportion is slightly higher. Children don't cope with heat as well as adults and are more prone to dehydration, especially when outside playing on a warm day. In order to remain healthy, we need to maintain our fluid levels.
For children between the ages of one and five years old, this means an intake of between 1.3 and 1.6 litres every day.
This amount includes the water content of food. On average, that means drinking between 0.9 and 1.2 litres of liquid a day. But how can we ensure that the children are drinking enough, and what should we be giving them to drink?
WATER
Water is by far the best liquid for hydration. Last year at Cowgate, we had a long spell of gloriously warm weather when most of our children chose to be outside and we had meals and snacks in the garden.
Jugs of water were kept in an accessible place all day and replenished regularly so the children could help themselves to it.
We tried to encourage the younger children to drink up too. However, we found that a lot of them were not drinking the water provided and we had to find alternatives that were not only acceptable to the children, but were also healthy. Here are some of the ways we found to keep the children hydrated.
MILK
Milk is a healthy drink, but if the children drink large amounts of it they will be filling up their tummies and may not eat their meals. They would then be missing out on some other vital nutrients in their diet.
Also, because of the calcium it contains, milk should be limited to around a pint a day - too much calcium intake and the body's absorption of iron is compromised. This can affect a child's development. Children under three years of age should have only whole milk, follow-on milk or if on a special dairy-free diet, a suitable alternative.
If you want to flavour the milk, use fruit purees instead of commercially produced milkshake ingredients as they invariably contain sugars and additives. Also limit having other sweetened milk drinks such as hot chocolate. They can be a special treat.
FRUIT JUICES
Fruit juices are healthy and a glass can count as one of the children's five a day. You should be aware, however, that no matter how much fruit juice is drunk in a day it will only ever count as one of the daily portions.
On the down side, the juices still contain sugar, albeit naturally occurring, and can also be very acidic. This can be detrimental to children's teeth, causing decay.
At Cowgate, we try to limit their intake of juices, and for our younger children we dilute the juices well. We only use pure fruit juices and not juice drinks, which usually contain added sugars and sweeteners.
TEAS
Chilled fruit teas can look very inviting, especially varieties such as pomegranate or blueberry. They have a wonderfully rich jewel colour and a lovely fruit taste. They are a great way to get the children to drink water, and they contain no caffeine or calories.
I find that you don't have to make them with boiling water and wait until they cool enough to put them to chill - just fill your jug with cold water, pop in the teabags, and put in the fridge until chilled. Stir every so often and squeeze the teabags to release the flavour and colour.
FRUIT
Fresh fruit also has a good water content and eating it can contribute to a child's fluid intake for the day. Melons, for example, are about 90 per cent water, and other fruits with a high water content include berries and citrus fruits. This is another way to ensure the children get their required fruit and vegetable intake.
Try to have a tempting variety for them to choose from and let the children help to prepare it. The fruit can be left as a kind of open buffet for them to dip into.
SORBETS AND WATER ICES 
Many fruits can be made into sorbets. Choose ones that are naturally sweet and you won't have to add sugar. All you have to do is prepare and chop up the fruit.
Freeze it and then put it into a food processor or blender until it forms a thick paste. Our children enjoyed this scooped into wafer cones, especially the summer fruit one.
ICE LOLLIES
These are a fun way for the children to get their fluids, and are very easy to make. They can be made with fruit juices, fruit tea, pureed fruit, and even milk, and you can use your imagination to make them more exciting. Try making multi-colour stripy ones - I used orange juice, apple juice and cranberry juice. You can also freeze small pieces of fruit through them.
SMOOTHIES
Smoothies are another good way to help meet children's five a day target, but as these drinks contain sugar and can be acidic, it is probably best to serve them at mealtimes.
Dilute them well with water, fruit juice or fruit tea to make them more refreshing, and keep an eye on the colour combinations of the fruit that you use. Too many different colours can look sludgy and unattractive. Try all red or orange fruits for a brighter, more tempting look.
June Graham is an early years practitioner at Cowgate Under 5s Centre, Edinburgh, www.cowgateunder5s.co.uk
MORE INFORMATION
There is lots of information online, but the source that I found best was a water intake tool, www.miniwebtool.com/ how-much-water-to-drink-a-day.
Other sources include: