This chapter presents the Rijnland case study area and water system, and analyses the hydrometeorological data sources for Rijnland used in the research. The Rijnland area, located in the western part of the Nedierlands, is a low lying area with most of it being reclamation lands from lakes and the sea. Rijnland Water Board, the organization which is responsible for water management in the area, applies strict rules to the water-level control in the canals. In Rijnland, the daily surface water balance is one of important information for operational water management by the Water Board. The soil map for Rijnland is available from two sources: European database and Dutch database. Rijnland area has many ground water observation wells; however, most of them are located near a canal which influences the shallow ground water head. The lowest ground water levels appear in the low-lying reclamation areas in the northeast and southern parts of Rijnland.