In the semi-arid lands of southern Kenya, a dynamic process of farmer-led irrigation has developed over the past two decades. It is characterised by short-term agreements to access land and water. Resident and migrant farmers, capital providers and local landowners have engaged in diverse partnerships to benefit from water and land along the Olkeriai sand river. This study aims to unravel which actors and motives drive the resulting highly dynamic forms of irrigation. Surveys, in-depth interviews and mapping exercises with farmers, capital providers and landowners were conducted over a period of 1.5 years. The results show that involved actors favour short-term lease and partnership arrangements and farmers frequently change fields along the river or leave the area and return. It is primarily the migrant farmers and capital providers who take decisions on when and where to move. They are informed by their experience with production factors, financial gains and losses, partner relations, or the ability to expand. We conclude that individualisation of land rights, migration, abundance of water, proximate markets, and rural-urban networks are instrumental to the emergence of this dynamic form of agriculture. Farmers have found a degree of security in flexibility, to access land and water in shifting fields and partners, rather than in property rights for specific plots. Yet, the short-term scope of these operations for monetary gains raises concerns about the sustainable use of land and water resources in the region.