In the hydrological cycle, water evaporates from the oceans, lakes and rivers, from the soil and is transpired by plants. This water vapour is transported in the atmosphere and falls back to the earth as rain and snow. It infiltrates to the groundwater and discharges to streams and rivers as baseflow. It also runs off directly to streams and rivers that flow back to the ocean. The hydrologic cycle is a closed loop and our interventions do not remove water; rather they affect the movement and transfer of water within the hydrologic cycle.
In 1969, Freeze and Harlan (Freeze and Harlan, 1969) proposed a blueprint for modelling the hydrologic cycle. In this original blueprint, different flow processes were described by their governing partial differential equations. The equations used in the blueprint were known to represent the physical processes at the appropriate scales in the different parts of the hydrological cycle.
From 1977 onwards, a consortium of three European organizations developed, and extensively applied, the Système Hydrologique Européen (SHE) based on the blueprint of Freeze and Harlan (Abbott et al., 1986a & b). The integrated hydrological modelling system, MIKE SHE, emerged from this work (see Figure 1.1)
Since the mid-1980's, MIKE SHE has been further developed and extended by DHI Water & Environment. Today, MIKE SHE is an advanced, flexible framework for hydrologic modelling. It includes a full suite of pre- and post-processing tools, plus a flexible mix of advanced and simple solution techniques for each of the hydrologic processes. MIKE SHE covers the major processes in the hydrologic cycle and includes process models for evapotranspiration, overland flow, unsaturated flow, groundwater flow, and channel flow and their interactions. Each of these processes can be represented at different levels of spatial distribution and complexity, according to the goals of the modelling study, the availability of field data and the modeller’s choices, (Butts et al. 2004). The MIKE SHE user interface allows the user to intuitively build the model description based on the user's conceptual model of the watershed. The model data is specified in a variety of formats independent of the model domain and grid, including native GIS formats. At run time, the spatial data is mapped onto the numerical grid, which makes it easy to change the spatial discretisation.
Figure 1.1 Hydrologic processes simulated by MIKE SHE
MIKE SHE uses MIKE Hydro River to simulate channel flow. MIKE Hydro River includes comprehensive facilities for modelling complex channel networks, lakes and reservoirs, and river structures, such as gates, sluices, and weirs. In many highly managed river systems, accurate representation of the river structures and their operation rules is essential. In a similar manner, MIKE SHE is also linked to the MOUSE sewer model, which can be used to simulate the interaction between urban storm water and sanitary sewer networks and groundwater. MIKE SHE is applicable at spatial scales ranging from a single soil profile, for evaluating crop water requirements, to large regions including several river catchments, such as the 80,000 km2 Senegal Basin (e.g. Andersen et al., 2001). MIKE SHE has proven valuable in hundreds of research and consultancy projects covering a wide range of climatological and hydrological regimes, many of which are referenced in Graham and Butts (2006).
The need for fully integrated surface and groundwater models, like MIKE SHE, has been highlighted in many studies (e.g. Camp Dresser & McKee Inc., 2001; Kaiser-Hill, 2001; West Consultants Inc. et al., 2001; Kimbley-Horn & Assoc. Inc. et al., 2002; Middlemis, 2004, which can all be downloaded from the MIKE SHE web site). These studies compare and contrast available integrated groundwater/surface water codes. They also show that few codes exist that have been designed and developed to fully integrate surface water and groundwater. Further, few of these have been applied outside of the academic community (Kaiser-Hill, 2001).
Applications around the world
MIKE SHE has been used in a broad range of applications. It is being used operationally in many countries around the world by organizations ranging from universities and research centres to consulting engineers companies (Refsgaard & Storm, 1995). MIKE SHE has been used for the analysis, planning and management of a wide range of water resources and environmental and ecological problems related to surface water and groundwater, such as:
· River basin management and planning
· Water supply design, management and optimization
· Irrigation and drainage
· Soil and water management
· Surface water impact from groundwater withdrawal
· Conjunctive use of groundwater and surface water
· Wetland management and restoration
· Ecological evaluations
· Groundwater management
· Environmental impact assessments
· Aquifer vulnerability mapping
· Contamination from waste disposal
· Surface water and groundwater quality remediation
· Floodplain studies
· Impact of land use and climate change
· Impact of agriculture (irrigation, drainage, nutrients and pesticides, etc.)
Graham and Butts (2006) contains a list of some easily accessible references for many of the application areas listed above.
User interface
MIKE SHE’s user interface can be characterized by the need to
1. Develop a GUI that promotes a logical and intuitive workflow, which is why it includes
– A dynamic navigation tree that depends on simple and logical choices
– A conceptual model approach that is translated at run-time into the mathematical model
– Object oriented “thinking” (geo-objects with attached properties)
– Full, context-sensitive, on-line help
– Customized input/output units to support local needs
2. Strengthen the calibration and result analysis processes, which is why it includes
– Default HTML outputs (calibration hydrographs, goodness of fit, water balances, etc.)
– User-defined HTML outputs
– A Result Viewer that integrates 1D, 2D and 3D data for viewing and animation
– Water balance, auto-calibration and parameter estimation tools.
3. Develop a flexible, unstructured GUI suitable for different modelling approaches, which is why it includes
– Flexible data format (gridded data, .shp files, etc.) that is easy to update for new data formats
– Flexible time series module for manipulating time-varying data
– Flexible engine structure that can be easily updated with new numerical engines
The result is a GUI that is flexible enough for the most complex applications imaginable, yet remains easy-to-use for simple applications.
