Operational management of regional salt-fresh water resources

In this PhD project (1.1.3) of water nexus, our aim is to develop new operational tools to be used for operational management of regional fresh water resources in low-lying deltaic areas with saline groundwater exfiltration. The developed tools can be used by water managers and operators to increase the operational efficiency of the system.

Saline groundwater exfiltration to surface water increases surface water salinization and degrades the water quality in these areas. As the use of surface water is less appropriate for agricultural, industrial and drinking water production due to salinization, freshwater diverted from a river is often utilised for flushing canals and ditches. The effects of climate change, sea level increase and fresh water availability increases the stress on deltaic areas resulting in questioning current fresh water management strategies.

In this PhD project, an advanced control method, namely, Model Predictive Control (MPC) will be developed to control the flushing operations in low-lying polders. MPC is a powerful control method that is increasingly used for managing water systems. The explicit consideration of constraints and multi-objective management are important features of MPC. MPC scheme developed in this project would be able to keep combined water quality and quantity set points while minimizing the fresh water used for flushing operations. 

Understanding the processes involved in the controlled system has a high importance for the development of MPC scheme. Therefore, at the beginning of the project, a simple test canal is going to be used to develop the controller. This phase would be followed by implementing the developed scheme to a real low-lying polder catchment (Lissertocht) in Haarlemmermeer polder (Fig.1). As can be seen in Figure 1, high spatial variation of salinity in this catchment (due to different saline groundwater exfiltration sources) would be an important challenge as an operational water management problem.

 

Figure 1 Schematic view of Lissertocht catchment and electrical conductivity (EC25) measurements of the ditches (Delsman,2014)

Using the knowledge and experience gained from the real case implementation of the developed control scheme, a general framework (modelling, measurement) for the control of salinity in similar areas would be provided at the end of the project.