Walking in hot, dry conditions
- Seeking information
- On the track
- Water loss and body temperature
- Surface water
- Other sources of water
- Food and dietary considerations
- Emergency situations
Internationally, Australia has the reputation of being the sunburnt country. Most of our land is hot for much of the year and on average, Australia is the driest continent on Earth. It is inevitable that walkers in nearly all parts of Australia will face hot, dry conditions at times. Even in the cooler and wetter parts of southeast Australia, there will be times and locations where temperatures are high and available surface water is scarce or non-existent. The safety and enjoyment of bushwalking groups venturing into these conditions or encountering hot, dry conditions during trips relies on sound planning, the knowledge of how to handle such conditions, and the flexibility to modify plans.
Thorough research on the likely conditions in any given area at the time of year the trips are to be undertaken is essential for ensuring groups are properly prepared for the conditions. The Bureau of Meteorology provides average temperature and rainfall information for all parts of Australia by month of the year, which can be an excellent guide to likely temperature and rainfall. This information is also printed on some topographic maps.
However, in most cases, the best sources of local knowledge will be employees or contractors engaged by the department responsible for managing the area proposed for the trip. A telephone call to the local rangers’ office will usually connect you with someone who has detailed knowledge of the area and current information on the likely availability of water, whether creeks are flowing, alternative sources of water and so forth. These personnel tend to work in such jobs because of their fundamental love of the land and out of concern for its management and conservation, so they are mostly more than happy to assist bushwalking parties to get the most out of their trips. Also, such personnel are usually an excellent source of advice on road conditions, access, scenic highlights and similar issues which can be the difference between a smooth running enjoyable trip and one which is beset with logistical problems.
If you are seeking information from these sources, it is worth commencing your work a few weeks prior to the planned trip date. Usually there will be one best person to contact and it may take a while before they are available to speak with you due to the nature of their work.
In planning all trips, you need to be aware of all conditions likely to be encountered and set the location and itinerary of your trip accordingly.
You will need to plan for alternative water sources in the event that creeks are dry, tanks are empty or springs have ceased flowing. For some trips, there is no real alternative to organising a water drop, whether put in by yourself or by others. Some rangers are prepared to organise water drops, particularly for remote parks with low visitation levels. In many parts of Australia, water from bores can be unreliable due to inconsistent availability, or it may be unsuitable for drinking because of fouling by stock or a high mineral content.
Try to plan trips to allow for a siesta during the hottest part of the day. Walking when temperatures exceed 30°C is generally unpleasant and your planning should determine how much of the day is likely to be above these temperatures, and should be reserved for an extended rest period. Getting up as soon as it is light, and walking in the early part of the morning, and again in the early evening can be very pleasant. Walking at night if the country is open enough and there is sufficient moonlight opens up a whole new dimension of the bush which we often miss. Try to avoid steep climbs in the hottest conditions, and allow for shorter stages and slower times than would apply in cooler conditions.
On the track
Walking in hot weather is generally tough on the feet if the ground is hard or rocky, while soft sand means slow, tiring walking. A lot of flat, semi-desert country has very subtle features, so check map and compass frequently, especially if following man-made features which can change significantly from those marked on maps. It has been estimated that it can take more than 20 years for a single vehicle movement off the track to completely disappear—so new tracks can appear rapidly, and old ones disappear very slowly. Navigation in these areas can be difficult, and reorienting yourself difficult and time consuming, so it is best to avoid becoming lost in the first place. Use of a GPS can be helpful in these circumstances.
Heavy rains or thunderstorms can cause creeks to rise rapidly to dangerous levels, but as they usually subside just as quickly, it is better to wait rather than attempt to cross a swollen creek. Because of the danger of flash floods, avoid camping in dry creek beds. Desert storms can be very isolated, and it is possible to encounter a flash flood many kilometres from the site of the rain—in fact it may not rain at all where you are, yet creeks can rise without warning. Dry areas are attractive to ants and other insect pests, so check the site carefully prior to setting up camp. Use sand or toilet paper for washing dishes to preserve water. Always clean dishes after use or your gear will be smothered with ants.
Dust or sandstorms can reduce visibility significantly and it is generally best to set up camp and wait for these to pass.
Water loss and body temperature
The ability to sweat increases with repeated exposure to high temperatures. The highest sweating rates are attained by a person acclimatised through prolonged heat exposure. You lose more water, not less, as you acclimatise, so water saving comes from understanding the environment and avoiding activity during hot periods.
Safe body temperatures are maintained by the evaporation of sweat from bare skin, so cooling is not as efficient via sweat-soaked clothing. On a really hot day water lost through sweating may reach 1 litre/hour. Table 16.1 gives an indication of the minimum daily water requirement to maintain body fluid when resting in shade at a given temperature. Walking may double this water requirement.
A slight increase in body temperature is not unusual among people exerting themselves in the hot sun. A body temperature of 38°C or even 39°C can be tolerated, but higher temperatures can lead to serious injury or death. Once air temperature rises above skin temperature, heat loss can only be achieved by sweating.
|Mean temperature (oC)||20||25||30||35|
|Water requirement (litres)||1.2||1.4||2.5||5.1|
Clothing should be lightweight, light coloured or white, and loose fitting. It should cover as much exposed skin as possible. Cotton garments are better, as synthetics generally do not breathe as well, and can be uncomfortable and cause skin rashes.
Covering your head and neck with a wide-brimmed hat, shirt collar and/or neck cloth are sensible, if not essential. Solid boots are advisable, together with thick woollen socks which absorb a lot of moisture before feeling wet.
Gaiters are useful to prevent the entry of sand into boot tops, and to protect lower legs against prickly bushes. Your feet should be washed whenever an opportunity arises, and socks can be ‘sterilised’ daily by laying them in the sun during rests and lunch stops. Dusting your feet with foot powder is also worthwhile.
It may be worth taking a fly net, as continuous use of insect repellents on long trips may cause skin irritation and could reduce the ability to sweat.
Equipment is generally similar to that carried in temperate conditions. Extremes of temperature occur in desert areas, ranging from hot days to very cold nights. A light-or medium-weight sleeping bag is normally carried, plus spare clothing to adjust body insulation according to night temperatures. Tents are needed for the same reason, and to provide protection from insects, cold winds and the occasional rainstorm. Tents should be fitted with mosquito nets so that the flaps can be left open for ventilation. A water bag and water bottles capable of carrying nine litres are essential for every party member in outback regions, particularly in warm weather. A rubber or plastic tube with a 5 mm bore and about 1 m long is useful for sucking up water at soaks.
In desert areas available water often contains salt, or other minerals. It may also contain pollutants or organisms such as blue-green algae which make it unsafe to drink. Salt in excess of body requirements can be eliminated only by increasing the water intake. This explains why salty water is undrinkable. In practice, the salt content of water must be below 1% if the water is to be drinkable. If it happens to rain, a large sheet of thin polythene (e.g. 4 × 2 m) is useful. It can be put out to catch the rain, and can yield several litres from a millimetre of rain. A sponge is useful for collecting the water. Issues of safe drinking water are discussed in Chapter 28.
Even though the nights in the desert can be cold, dew usually occurs only for a few nights following rain. Dew can be collected from some tents by turning up the eaves with sticks to form a shallow gutter around the tent roof and then either sopping it up with a sponge, or scraping it into the gutter with the blade of a knife. A two man tent will yield a cup of water (flavoured with proofing). Another method of collecting dew is to spread a plastic sheet on the ground.
Water from bush dams and soaks is often polluted by animals so purification is therefore essential, as described in Chapter 28. The appearance of muddy water can be improved by letting it settle overnight in a billy or water bag, or by adding a piece of charcoal. The taste of stagnant water may be improved by aeration, e.g. by whisking it with a twig or by pouring if from container to container. Encourage members of your party to drink freely and copiously from the time they arrive at camp until they leave, especially in the morning, and then to drink little and often during the day. A salt and mineral replacement may be required, particularly by people with a high salt intake in their diets and who are unaccustomed to heavy sweating in hot, dry conditions. One level teaspoon of Staminade (or similar product) per litre of water is sufficient.
Other sources of water
A careful inspection of the terrain may indicate some possible sources of subsurface water (Figure 16.1). This is generally found where there are signs of vegetation—the greener the vegetation the better the chances of finding water. The base of a hill is the most likely spot. Small soaks can be found on the shoulders of escarpments/cliffs that are sheltered from the sun and support green growth.
Observe bird movement in the afternoon, as they are a good indicator of the direction of water.
Dry creek beds or water holes often hide water up to 60 cm below the surface. A shallow hole dug at the lowest point on the outside of a bend may produce a seepage of water into the hole.
When roots of trees or scrub and leaves are placed in a plastic bag they will lose water through transpiration, and the subsequent condensation can produce drinkable water.
Two plants common in desert regions following substantial rain are parakeelya (Calandrinia sp.) and portulaca (pigweed). Parakeelya are small succulent plants mostly with pink flowers and short stems. Both are edible and will allay thirst if chewed, as the leaves contain a large percentage of water.
Trapping water from live vegetation
In hot conditions, it can be possible to capture up to about 300 ml of water per 24 hour period by enclosing in a large garbage bag bunches of foliage attached to living branches of trees. The bags should be attached carefully and any puncture holes sealed with tape and the bag sealed as tightly as possible around the branch. Aim to enclose as much vegetation as possible. Experience has shown that generally the young, actively growing parts of eucalypts and introduced European trees work best, followed by conifers and heathy bushes, etc. Bags should be attached early in the morning, and placed in positions where the branch will be in as much direct sun during the day as possible. The main disadvantage of this technique is that in certain circumstances it can kill the branches of the trees used. It is worth reserving this method for emergencies.
Solar water still
Extensive experience with solar stills in arid conditions suggests that they are generally ineffective in producing any useful quantity of water. As they produce much less water than the method of attaching bags to trees, and probably cause more environmental damage, it is hard to recommend devoting the time and effort required to build one.
Food and dietary considerations
Clearly the primary issue in hot, dry conditions is providing sufficient water to prevent dehydration. Work undertaken at the Australian Institute of Sport in Canberra has shown that even very low levels of dehydration lead to significant losses in physical efficiency. Typical figures suggest that 2% dehydration can lead to reductions in physical efficiency by up to 20% among elite athletes. For a typical 70 kg walker, this translates to a loss of about 1.4 litres of fluid. Our experience shows that walkers can easily lose 6 kg (6 litres of fluid) in a single day, so preventing dehydration is both paramount and difficult.
It has often been said that moisture-laden food is best in hot, dry conditions as it is more palatable and easier to eat. While probably true for many walkers, this preference may derive from the substantial levels of dehydration affecting most walkers in hot, dry conditions.
Dehydration is best addressed with water, not moisture-laden food. If prevention of dehydration is properly tackled, the need for relatively moist foods for palatability becomes much less of an issue. Moisture-laden foods are heavy. Dehydrated food is lighter, so additional water can be carried.
Chapter 27 discusses food and outdoor diets in more detail, including a section specifically on food for hot, dry conditions.
If you think you are lost, stop and apply the ‘lost’ procedure (see Chapter 38). It is dangerous to continue in the hope that water will be found. Note the following points:
- get out of the sunlight into shade, and up off the hot ground
- keep your body covered, especially your neck and head
- minimise muscle action during intense heat
- wear dark glasses if you have them
- drink when thirsty but do not eat, as this uses up water for digestion
- keep your mouth shut—minimise talk
- analyse the situation and resources available—food, clothing, shelter, first aid and signals
- a smoky fire or a flashing mirror can be seen from a great distance by a search party or an aircraft in flat, arid country
- do not travel unless absolutely necessary and then only in the cool of the early morning and late evening or night if conditions permit
- walk slowly and rest often. In critical situations save urine, not for drinking but for cooling the body.
One important principle you should always follow when travelling by vehicle in desert country is to make sure that the authorities or some responsible person knows of your destination and when you are due there. Then, if your vehicle becomes bogged or breaks down, stay by it. Many lives have been needlessly lost in outback areas through failure to do this.