Quoted from: https://github.com/UW-Hydro/Reservoir_Model 

####Model Overview: This repository is public source code for a simple two-layer reservoir model. The model does a simple mass and energy balance for a reservoir with two distinct layers: the epilimnion (surface) and hypolimnion (below surface). Inflow is partitioned based on the calculated densities of the incoming water, epilimnion, and hypolimnion. The net surface energy is calculated with VIC-derived incoming energy and an energy subroutine from RBM. The core subroutine (reservoir_subroutine.f90) calculates the change in temperature of each layer based on net change in energy from advection, surface energy (epilimnoin only), and diffusion (see conceptual model below). A more complete documentation of model development and equations can be found here. The model allows for measured releases from a spillway (epilimnion) and penstock/sluiceway (hypolimnion) to be uploaded. The model code comes with no guarantees, expressed or implied, as to suitability, completeness, accuracy, or any claim you would like to make.

####Conceptual model of stratified reservoir:  ####Conceptual model of two-layer mass and energy fluxes*: 

*parameters (i.e. As, Kz, etc.) are defined in the "Documentation" document

####File descriptions:

• Block_Energy.f90: parameters for energy subroutine (originated from RBM Block)
• Block_Reservoir.f90: parameters for the model
• Block_Flow.f90: parameters for the "flow_subroutine.f90" (continuity/mass balance equation)
• reservoir.f90: main program that calls each subroutine
• density_subroutine.f90: calculates density of incoming river flow, epilimnion, and hypolimnion
• flow_subroutine.f90: continuity/mass balance equation - calculates the flow into hypolimnion and hypolimnion (based on the density) and calculates change in volume of each layer
• Energy.f90: RBM's energy subroutine to calculate surface energy exchange
• reservoir_subroutine.f90: calculate transfer of energy between layers through advection, diffusion, and surface energy
• input_file: file path of line 1- comments, line 2- flow in to reservoir, line 3-flow out reservoir, line 4-energy flux (from VIC), line 5-measured stream temperatures, line 6-measured releases
• reservoir_file: file with information about each reservoir to be modeled. line 1-column names, line 2 to n-rows of data. Start node is upstream point (where water enters the reservoir), end node is downstream point (where water exits the reservoir)
• makefile: make file with code to compile all the fortran code and to remove the compiled fortran code

####Model code flow diagram: 

####To run the model: Note: This must be run from the terminal while in the folder with all the fortran code. You must have gfortran installed on your machine. This also assumes input_file and reservoir_file are ready and all files for the input_file are present.

1. enter "make clean" - remove any old compiled fortran code
2. enter "make" - compile the fortran code
3. enter "./reservoir input_file reservoir_file"