The hydrological model TopNet was developed at NIWA and is commonly used in New Zealand. Typical applications include flood forecasting, irrigation planning and estimates of climate change impacts on river flows.
TopNet is a semi-distributed hydrological model for simulating catchment water balance and river flow.
TopNet uses a modelling approach which combines an understanding of hydrology and soil science to calculate the water available in various locations (soil, lakes, streams) over time. In simple terms, TopNet is a catchment water-balance calculator.
Using this computer-based model scenarios can be tested based on specific ‘variables’, such as size of reservoir, amount and timing of rainfall, size of the catchment, amount and timing of irrigation, and so forth. TopNet allows calculation of how these variables will interact over time. TopNet has resulted in the following:
|Latest Version||Version 11 (2011)|
|State of Development||Stable Release|
|Current Development Activity||Coupling with a glacier component and developing a retrospective streamflow assimilation scheme.|
|Intended End Users||Highly trained personnel / In-house specialist|
|Spatial Extents||Local (i.e. Catchment or District), Regional, National|
|Steady State or Dynamic||Dynamic|
|Level of Integration||Environmental|
|Key Input Data||Land Use, Land Cover, Rainfall, Temperature, Potential Evaporation Topography, soils|
|Input Data Formats||netcfd|
|Key Output Data||Runoff, Drainage Soil moisture, snow|
|Output Data Formats||netcdf|
|Open/Closed Source||Closed Source|
|Operating Systems||MS Windows, Linux|
|Software Needed||netcdf libraries|
|User Interface||Other (please specify) Command Line|
|Ease of Use||Difficult There is a significant training overhead to learn to use Topnet. Specific implementations customised for users are much simpler to operate, and more limited in functionality.|
|Use in Policy Process||Plan (Policy Formulation)|
User manual and help files available on the NIWA website (https://one.niwa.co.nz/display/HYPRO/TOPNET+++Model).
|Support||On research collaboration basis|
|Programming Language||Fortran and C|
|Methods included for calibration and validation||(1) Manual calibration (2) NLFit: a parameter fitting Windows-based program that uses optimal parameter search algorithms.|
|Methods included for managing uncertainty||Monte Carlo simulation: a large number of different parameter sets are tried and the best set selected based on an objective function (e.g. the Nash Sutcliffe criteria).|
|Keywords||flooding, irrigation, climate change, rivers, flow|
Clark, M.P.; Woods, R.A.; Zheng, X.; Ibbitt, R.P.; Slater, A.G.; Rupp, D.E.; Schmidt, J.; Uddstrom, M.J. 2008:. Hydrological data assimilation with the Ensemble Kalman Filter: use of streamflow observations to update states in a distributed hydrological model. Advances in Water Resources: 31, 1309-1324.
Subsequent requirements extended the modelling window to mid-2014 and the TopNet model was re-run to include this additional time period.
Mostly used in New Zealand, but with applications overseas, such as in the United States of America and Chile.
A pressure-state-impact model for freshwater flows with example application to Canterbury, NIWA Client Report No: 2017071CH, Prepared for Ministry for the Environment, March 2017.
Irrigation forecasting - Wamakariri River (2009) - http://www.niwa.co.nz/freshwater/projects/forecasting-irrigation-potential-a-case-study-in-the-waimakariri-river-catchment