Severe flooding in Bolivia that began in December 2007 has affected more than 20,000 families and killed more than 30 people. The Bolivian government has declared a state of emergency.

Two MapAction volunteers, Emese Csete and Chris Ewing, deployed to Bolivia on 26 January in response to a request for emergency mapping support from the U.N. Office for the Coordination of Humanitarian Affairs. Here are extracts from their reports during the mission.

Sunday 27 January

Dawn was breaking as we approached La Paz this morning, and we could get a sense of the extent of the flooding from the air. There were several overflowing rivers coming down from the mountains, and swathes of mud indicated that the flooding had already receded significantly. In the distance we could see large pools of muddy water in many areas. And that's just in the La Paz area.

We landed at seven-ish Bolivian time, only to find our baggage hadn't make it (sigh). The airport will call us tomorrow to say whether it has arrived.

We meet two members of the United Nations Disaster Assessment and Coordination (UNDAC) team who were heading to some local offices for a briefing, where they hoped to find out more. They will be briefing us on their return at lunchtime. We've managed to borrow a power adapter. Note for next mission - put an adaptor in our hand baggage. Also wishing we'd pocketed a change of underwear!

Chris's good Spanish is proving invaluable and he is getting us by very well, even discussing Internet settings and so on. There's Internet at the hotel but it's not reliable and not sufficient for downloading the rest of the GIS data from the ftp site. But the UNDAC team say that the UNICEF offices where we'll be working are well equipped. Our first situation map, produced from an OCHA situation report, was ready to issue by 6.30 pm.

Getting used to the 3,600-metre (11,800-foot) altitude, I'm feeling a bit dazed, but that's probably also tiredness from the 26-hour journey. Chris has learnt the hard way that he can't run up stairs here (he felt afterwards like he'd run for half an hour)!

Monday 28 January

We have been given space in the UNICEF offices for the time being. Great facilities, including wireless Internet and lots of plug adapters (phew!). The U.N. team is very organised and has given us local phones and SIM cards, taxi vouchers and so on. This makes up in part for the annoyance of not having the rest of our technical kit with us yet - hoping it will arrive this morning.

Max, the UNDAC team leader, has travelled down country to assess the situation there. The rains have caused relatively few deaths and have already receded somewhat. However, they have caused wide ranging problems: displaced people, contaminated water supplies, destroyed crops. And on top of it all many roads have been affected, making delivery of aid much more difficult.

The worry is that the rainy season is not yet over. So the aim now is to help to get a good picture of the current situation, as an aid to planning for further flooding if it happens.

It remains unclear which department (district) is worst affected at the moment. It depends if you talk to the national or regional authorities. The best way to find out is to get out and see, hence Max's departure for the field. An on-site ops coordination centre may be set up in one of the worst affected areas, but we await developments.

Meanwhile back at the ranch we are grappling with GIS data as a preliminary to producing large-scale situation maps. The topographic base map data we have been offered is fiddly to re-format so that our GIS software can read it: a quite typical problem that we will find a way around with some help from our British-based team.

Another vital "layer" of GIS data comprises the boundaries of the administrative districts and communities, so that we can code and map the situation information (like numbers of people affected in each place) as it comes in from the field. Andrew, the OCHA information manager, is hard at work on this set of data.

As an aside, Chris and I went out to grab a bite to eat and were trapped in the cafe while a torrential downpour descended. I've never seen it rain so hard in my life: a glimpse of how suddenly floods can occur.

Tuesday 29 January

We've had a busy day! We started by mapping the affected families data from the National Emergencies Department, for each district. We also prepared some maps for a presentation by the U.N. Disaster Assessment and Coordination team leader to the chiefs of the ministries.

The decision was taken this morning for Emese to travel to Santa Cruz (about 500 km east of La Paz, where the Bolivian altiplano descends into the Amazonian basin) with three of the UNDAC team, and work from there until Friday. Meanwhile, Chris will continue to work from La Paz.

Mid-morning we learned that our missing luggage, including the A3 printer, was at the airport but was being held in customs. After two hours at the customs office, Chris left Emese in the airport for her 6.30 p.m. flight to Santa Cruz.

On reaching Santa Cruz, insights were gained on the challenges of information management on the ground. It appears that the military and civil authories do not yet hold joint coordination meetings. There is apparently some good situation data in terms of affected areas, needs assessments and relief activities under way. This is being collected at the community level: Although we do not have map data of the community boundaries, we are aiming to aggregate it to municipality level, which will enable us to create a spatial picture of what is going on even though not at the level of detail we would like.

It seems likely that the rains - and flooding - will continue until March. Apparently the weather models run by the government, which have proved accurate in the past, forecast two further "waves" of flooding in the coming weeks. Floods in Bolivia are becoming a more common occurrence, it is claimed, as a result of the increased frequency in recent years of the La Niña climatic phenomenon. This stretches the government's capacity to deal with the outcomes, so international help is very important.

On a lighter note, it's from one extreme to another here. After wafer-thin clear air up at La Paz airport (4,000 metres), surrounded by the Andes, I'm now down at 400 metres, surrounded by lush greenery, banging music from clubs near the hotel (thank heavens for earplugs!) and air so humid and dense that you can cut it with a knife.

Just glad that we finally got back our luggage - and spare clothes. I changed my socks at the airport as soon as I got my rucksack. After four days in them they were so vibrant that they leapt off my feet and started running around on their own.

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