1. GHOST (Generic Hydrologic Overland-Subsurface Toolkit)
MM-pihm is a distributed coupled surface-subsurface hydrologic open source code commonly used to predict the hydrological response of medium-size watersheds over period of months (Qu et al., 2007; Yu et al., 2013). GHOST is a reformulation of MM-pihm to perform multi-year simulations in large basins. Modifications and modules specifically developed in GHOST was directed by:
Increasing performance
Coupling fluxes capable of reproducing long-term continuous basin behavior
Capturing physical processes in Iowa watersheds
Robust algorithms

2. Improving computational efficiency OF the code
Code consistent with new version of Sundials
Parallelized with OpenMP
Variable time step (depending on Sundials convergence efficiency)
Restart option
Improved interpolation schemes
Improving computational efficiency OF the code

3. Development of mathematical expressions for lateral fluxes
Robust scheme for lateral fluxes in 2D surface elements
New formulation for lateral fluxes between 2D surface elements and channel

4. Development of mathematical expressions for vertical Fluxes
New formulation for infiltration, exfiltration and recharge models
New formulation to include temporary streams. Development of channel infiltration and exfiltration models

5. Development of specific models for IOWA watersheds
Hello
Development of specific models for IOWA watersheds
Lake module
Retention basin module

6. Lake defined in overland grid with inactive cells in space occupied by the lake.
Fluxes to lake include overland flow, precipitation, stream flow, groundwater flow and evaporation
Bridge head losses between lakes included
Rating curves to calculate outflow
Lake storage-depth relationship to compute lake depth
Lake module

7. Retention basin module
Implemented in river segments
Contribution from overland and stream flows
Groundwater contribution
Outlet rating curves
Project storage-depth relationship to compute lake depth
Evaporation and infiltration included

8. ET model
Root depth, vegetation height and crop coefficient as a function of time
Optional use of potential evapotranspiration from NLDAS
New model for winter processes considering soil temperature and reduction of infiltration in frozen soils
Implementation of Panday and Huyakorn (2004) model

9. Outputs No. File Purpose 1 Simulation_name.plt
Visualization of hydrological response in 2D elements 2
Simulation_name_R.plt
Visualization of hydrological response in river segments 3
Simulation_name_WaterBalance.plt
Integrated variables over the watershed area to compute water budget 4
Simulation_name_RiverFile.plt
Evolution of flowrate for selected river segments 5
Simulation_name_GWFile.plt
Evolution of groundwater for chosen elements 6
Simulation_name_Continuity.plt
Continuity file to check mass conservation 7
Simulation_name_Grid.plt
Actual mesh after internal modification 8
Simulation_name_CVODE.log
Output information of Sundials solver 9
Simulation_name_Performance.txt
Numerical performance of the simulation 10
Simulation_name_P_ProjectFile.plt
Evolution of project/wetland variables 11
Simulation_name_P_ProjectStats.plt
% time project is above and below given elevations 12
Simulation_name_L_LakeFile.plt
Evolution of lake variables