Your questions answered by our panel of travel experts

How do I purify water when I'm trekking?

I am going on a trekking holiday in northern Pakistan and I want to know if there is any easy way to purify or clean water that does not necessarily involve boiling it. I am sure to be drinking from local streams but do not want the hassle of having to make fires all over the place.

Molly Maxton

Newcastle

Dr Larry Goodyer writes: Bearing in mind that boiling for about five minutes is the most effective way to sterilise drinking water, there are two options open to you: either to use chemical sterilisers or a filtering device. The two most widely used chemicals by travellers are based on the halogens iodine or chlorine.

Of the two, chlorine tablets (Puritabs), are the most widely available, but iodine tincture or tablets can be obtained through chemists or specialist travel shops and is said to be more effective against certain organisms.

There are a few important points to remember . First, the water should be clear of organic matter, so strain off any sediment through muslin or special canvas bags called Millbanks bags. Then remember to leave the chemical in contact with the water for the required time, usually about 30 minutes depending on the temperature of the water.

Follow the directions on the package regarding the amount to use and any warnings. Iodine can taste quite nasty if you use the higher concentrations sometimes recommended, but you can purchase neutralising tablets or powders which remove the taste.

There are a wide variety of portable filters on the market for use by travellers to prepare clean drinking water. They range from relatively inexpensive pocket-sized devices for emergency use, to more sophisticated ceramic ones that require a good deal of hand pumping. They do have the particular advantage over chemicals in giving an instant source of drinking water, but can be expensive, require maintenance and some will only sterile a limited amount of water before replacement cartridges are required.

Dr Larry Goodyer is superintendent of the Nomad Pharmacy (3-4 Turnpike Lane, London N8, Tel: 0181-889 7014) which specialises in catering for travellers' medical needs.

How do I still make it to the Rio carnival?

Is there still time for me to get out to see this year's Rio carnival? I realise that there is not much time left but it would be great to see it once in my life. And having got there, will I be able to join in - or do you have to buy some kind of ticket?

Gareth Barrell

Portland

The travel editor replies: It is not too late to get to Rio: the main carnival action takes place in the days leading up to 24 February so you've still got about a fortnight to find a flight. You'll pay more to fly in at this time of year but the difference is not astronomical - you'll be paying somewhere between about pounds 540 and pounds 650 for a return ticket during the Carnival period. Try Journey Latin America (0181 747 3108) who will still be able to put together a package for you even at this late stage. They can offer a five-night package including hotels, transfer and a night in the sambodromo (the purpose-built stadium where the finest samba-schools parade) for pounds 763, based on two sharing. Add on the cost of the flights and the price per person will come to about pounds 1,300.

If you are travelling in on a flight-only basis, there are basically two ways to view the carnival. You can buy an expensive (upwards of US$100) ticket to sit in the sambodromo; tickets will probably be available from the ubiquitous local tour operators right up to the last minute, though they will become more and more expensive.

Otherwise you can simply hang around in the streets of the city, where exuberant parades of the lower-league samba schools are taking place. You'll find plenty enough atmosphere here. And if you fancy a bit of decadence in the evening, try out one of the sexually charged carnival balls, for which tickets are available from about US$80.

How to rent a barge in the Netherlands

Help! We are keen to drive to the Netherlands for a week's break and wish to rent a house or maybe a barge. No companies seem to rent holiday cottages in Holland. We will be a large party of two families, with bicycles.

Clare Parsons

Leytonstone

The travel editor replies: Whenever you mention holiday homes in the Netherlands, the first thing that the Dutch will tell you is that you should stay at one of the famously Dutch holiday villages (ie Centre Parks or Gran Dorado). The accommodation ranges from modern bungalows to little wooden houses, and are nicer than you probably think.

However, there are other options. Firstly, in the eastern, northern, and southern parts of Holland there are farms which have holiday cottages on their land. Secondly, there are lots of options for staying on boats: either traditional sailing boats which accommodate 8-12 people, or barges which accommodate even larger groups. Finally, there are also self-catering huts on campsites which are good for touring cyclists.

If you want detailed information on how to book these, you need to write to the Netherlands Board of Tourism, PO Box 523, London SW1E 6NT. Unfortunately the details are all in Dutch, though fairly self-explanatory. There is no simple, centralised booking system - each house is accompanied by a specific local number you have to call.