Delta Life 8

4 DELTARES, OCTOBER 2017 DELTARES IN BRIEF In the early morning of 29 May, strikingly high waves were suddenly observed along the Dutch coast. This 'meteo- tsunami' was caused by an active line of thunderstorms, below which there was a change in air pressure that was clear to see on the systems of the Dutch meteorological service, the KNMI. 'These types of waves are not uncommon but they are not often noticed because the water level is low, or simply because there aren't many people on the beach,' explains researcher Deepak Vatvani. 'Phenomena like this have also been seen in other countries. It would be good to find out whether they will be more common in the future and what the risk is if the beach is busy.' METEO- TSUNAMI IRON MAKES FERTILISERS LESS HARMFUL IMPROVEDWATER QUALITY IN LAKE TOBA The water quality of Lake Toba in North Sumatra, one of the largest and deepest lakes in the world, is rapidly worsening. In the Lake Toba Tourism Master Plan, the government of North Sumatra has stated that the water quality and ecosystem of the lake are important. Not only for tourists, but also for the health of the people who live around the lake. On behalf of the World Bank, Deltares is working with North Sumatra on the establishment of a plan to improve water quality. Researchers are identifying both the problems and possible solutions. It is not easy to explain the mechanisms underlying the decline of water quality in such a large and deep lake. This study therefore looks at the entire catchment area of ​the lake. 0 10 20 40km Sungai Downstream Siruar Silau Piasa Upstream Siruar Samosir Luar WS Danau Toba Piasa 160 km 2 Downstream Siruar 2,015 km 2 Upstream Siruar 2,030 km 2 Silau 1,275 km 2 Danau Toba 1,130 km 2 P. Samosir 653 km 2 di Luar WS 943 km 2