A mathematical programming approach to restore the water balance of the hydrological basin of Lake Koronia
Over the last four decades Lake Koronia, part of the Mygdonia Basin, operates under a negative water balance due to poor resource management and planning decisions. Lake Koronia is a Ramsar site in northern Greece that has experienced pronounced ecosystem degradation over the past 30 years associated with water level reduction and nutrient loading from agricultural and industrial activities. The objective of the present study is the optimal design of an environmental policy for theoretical and potentially in practice return to a sustainable state of the watershed of Lake Koronia and recommend a rational water resource management plan for the area to promote and support development. The use of mathematical modelling tools can assist in making the right decisions with respect to the water management. The increased complexity of simply managing ecosystems, due to many overlapping factors that affect the water balance, impedes the derivation of the optimal policy to address the problems. This paper presents an optimisation model that takes into account all potential investment options that will allow the restoration of the lake and surrounding area to a sustainable level, and determines the optimal operating policy to allow the ecosystem to recover while maintaining the financial stability of the area. Investment options include the transfer of water from larger water sources, creation of irrigation networks and canals, provision of subsidies to promote alternative land use for agriculture and others. The restoration of a sustainable positive water balance for the basin is possible even if future climatic conditions become more arid than the current. Critical aspects are crop manipulation, irrigation networks and a policy to manage water as a commodity rather than an unlimited resource.