Ing. Klaas Oostindie, ESG staff member, died on January 9^th at the age of 64. In September 2020, Klaas was diagnosed with cancer and unfortunately physicians realized that the cancer was untreatable. Over the last 44 years, Klaas had worked in Wageningen at the Institute for Land and Water Management Research (ICW), the DLO Winand Staring Centrum, Alterra, WENR and Wageningen University & Research.

He started his career at ICW around 1976 in the Mathematics Department. He was a computer support assistant with special interests in programming, statistics and data analysis. Klaas rapidly grew into his job and worked at the forefront of rolling out a central computer system at ICW, the well-known Digital Equipment VAX environment. Klaas provided guidance in word processing techniques and helped to develop the first generation of computer programs for researchers working on soil and water-related issues.

In the mid 80s, Klaas started to collaborate more intensively with several ICW researchers like Jan van Bakel, Pim Rijtema, Koen Roest and Hans Bronswijk. Through these collaborations, Klaas developed an interest in studying and optimizing surface water level management in the Netherlands and in Egypt. He assisted in investigating shrinkage and swelling processes in heavy clay soils, and his related contribution to the PhD work of Hans Bronswijk was indispensable. During this period, he also became a formal research assistant in the Soil Department of the ICW.

In the 90s, Klaas further expanded his research interests and became involved in different research projects and programs focusing on soil erosion in Limburg, occurrence and impacts of soil water repellence, as well as preferential flow and transport processes. This research was carried out in close cooperation with Louis Dekker, Coen Ritsema, Jos van Dam, Rob Hendriks, Jannes Stolte and Erik van den Elsen, amongst others. As a result of his research interests, Klaas became more and more involved in publishing the related research results in international scientific journals and presenting results to audiences at various national and international workshops and conferences.

Between 2000 and 2015, Klaas realised that he enjoyed fieldwork and became seriously involved in many field and monitoring campaigns across the Netherlands and abroad. These campaigns were carried out to better understand soil wetting and drying dynamics in places like peat dikes, golf courses and soccer fields, as well as in various arable land types. Based on the results of these studies, researchers designed and tested ways to more uniformly wet soil systems, both in the lab and in dedicated field trials. Data collected were analysed and published by Klaas together with Jan Wesseling, Jan van den Akker, Demie Moore, Violette Geissen and many other researchers from WUR and elsewhere. Publications (co)authored by Klaas have been cited thousands of times, resulting in an impressive h-index.

Five years ago, Klaas decided to continue his career in the Soil Physics and Land Management chair group (SLM) of Wageningen University & Research. This was a logical choice since several of his old colleagues made the same move from Alterra/WENR to SLM such as Louis Dekker, Violette Geissen, Jan Wesseling and Coen Ritsema. This new opportunity provided Klaas continuity in his work. He was happy to be reunited with his old colleagues to further explore scientific horizons. This new move allowed Klaas to work more closely with PhD students, which he really liked to do. He helped many students with editing and enhancing the quality of their theses over the last couple of years, which was highly appreciated by staff members and students alike. In addition, Klaas also actively designed and maintained several websites for large international research projects coordinated by the SLM group.

Working with Klaas was nothing less than a privilege. He possessed a number of unique personal qualities that were ideally suited for research and his enthusiasm for science was contagious. We will remember Klaas as a very kind and amiable colleague who often kept to the background but when he spoke, he made sense. He was easily approachable and always willing to assist anyone asking for help and advice. Klaas was a lot of fun to be around, not only at the office but during numerous work trips to countries like the USA, Fiji, Samoa, Russia, Estonia, Greece, Spain, and Sweden. We have so many great memories. We will miss his knowledge, readiness to help, and dry humour, not only as a colleague but also as a friend. Coen Ritsema, on behalf of the Soil Physics and Land Management chair group