The long running border dispute between Malawi and Tanzania concerning their lacustrine border has flared up again. The dispute centres on Lake Nyasa, as it is known in Tanzania, or Lake Malawi as it is known in Malawi. A recent Tanzania government administrative map of regions and districts indicates that the border runs down the middle of the lake. Malawi’s interpretation is that all waters between Malawi and Tanzania are theirs.

Malawi’s claim is based on an 1890 treaty between Germany and the United Kingdom. After Tanganyika came under British control after World War I, the lake was administered from the Malawian side by British authorities. The border dispute has arisen more than once since independence, the first time being in 1967. Tempers in the current dispute have been ebbing and flowing since 2012, when Surestream started exploration activities on the lake.

Mediation was attempted under the leadership of Joaquim Chissano, former president of Mozambique, which also shares part Lake Malawi. These talks collapsed in disagreement over basic legal issues in the first half of 2014. Since then there has been no substantial progress made. Chissano tried to fudge a compromise, whereby the countries would agree to share the lake and try to tackle border delimitation at a later stage.

In response to the map issued recently, Malawi’s Ministry for Foreign Affairs in the past fortnight raised its objections directly with its Tanzanian counterpart, but has yet to receive a reply.

Tanzania is quite serious about its claims and is unlikely to back down dramatically. Even before the publication of the new map, it has challenged any maps in the media representing Malawi’s claim. Most recently in November 2015 the government spokesman, Assah Mwambene, forced a twitter user to remove a link to such a map. In 2013, he challenged a map shown on a CNN report.

But at the same time, the government is unlikely to want to provoke a major dispute. Surveying activities have been undertaken over the past seven years at least by Syracuse University of the United States. Though strictly speaking not searching for oil, the data generated – shared with both governments – will have great value in identifying prospects. The dispute may be enough to scare off prospectors from the lake until a resolution is found.