STEM-SM combines a simple ecosystem model (modified version of VSEM; Hartig et al. 2019) with a soil moisture model (Guswa et al. (2002) leaky bucket model). Outputs from the soil moisture model influence ecosystem dynamics in three ways. 

(1) The ratio of actual transpiration to maximum evapotranspiration (T/ETmax) modifies gross primary productivity (GPP).

(2) Degree of saturation of the soil (Sd) modifies the rate of soil heterotrophic respiration.

(3) Water limitation of GPP (by T/ETmax) and of soil nutrient availability (approximated by Sd) combine with leaf area limitation (approximated by fraction of incident photosynthetically-active radiation that is absorbed) to modify the allocation of net primary productivity to aboveground and belowground parts of the vegetation.

Ecosystem dynamics in turn influence flows of water in to and out of the soil moisture stock. The size of the aboveground biomass stock determines fractional vegetation cover, which modifies interception, soil evaporation and transpiration by plants.

Concept: Pi-Cheng Chen

Develop a daily time step simulation model that consists of a reservoir with a single inflow and single outflow (release)

Use units of million m3 and include any necessary parameters (e.g., capacity k) as separate adjustable variables

Implement the standard linear operating policy (SLOP). 

Assume the reservoir is 500 mcm (k=500). 

Develop yield-reliability results for a target (T) delivery values of 1, 3, 5, and 7 mcm/day.3 

(The mean inflow for the time series is 34.8 m3/s, or 3.0 million m3/day.)

The standard linear operating policy provides a basic rule for reservoir release.