Talsim Documentation

In a hydrological model, the behavior of the system is driven by external influences—commonly referred to as forcing data or loads. These include:

•Precipitation

•Temperature

•Evaporation

•Inflow from upstream sources

•Pollutant or substance loads

•Water discharge & extraction

Talsim offers a flexible framework to incorporate these real-world hydrological inputs into the model. This chapter provides an overview of the available methods for defining and connecting such inputs to the model system.

How Input Data Enters the Model

Water and other loads are introduced into the system primarily via the following System Elements:

•Sub-basin (Catchment): Represents natural hydrological input (rainfall-runoff model).

•Point Source: Represents external inflows or pollutant discharges with known hydrographs.

•Consumer: May act as an inflow if a water supply from outside the modeled system is included.

•Storage: Can introduce additional inflows via precipitation inputs scaled to the water surface area.

Water losses from the system can also occur and are modeled through:

•Consumer and Diversion elements (e.g., water use, withdrawals)

•Storage elements when evaporation modeling is enabled

•Sub-basin elements, via runoff partitioning, where single components such as urban runoff or deep baseflow are routed out of the system

Defining Forcing Data in Talsim

Regardless of the type of input—be it temperature, precipitation, evaporation, or inflow—Talsim provides two main methods to define time-dependent data:

•Working with Patterns
For repeating inputs (e.g. seasonal water demand, monthly precipitation patterns), Talsim allows the definition of Patterns (daily, weekly, or annual).

•Working with Time Series
For observed or simulated data, Time Series provide detailed chronological records of inputs with specific timestamps.

In most modeling cases, input data will be defined using one of these two formats. This approach is consistent across input types and system elements.

Evaporation Components: A Third Option

In addition to using Patterns or Time Series, evaporation can also be modeled dynamically using an Evaporation Component. This component calculates evaporation based on geographical and meteorological parameters such as:

•Latitude

•Temperature

•Wind speed

•Sunshine duration

These meteorological inputs are themselves introduced into the model as Patterns or Time Series. This option is especially useful if no evaporation data is available directly.