NZWaM - Surface water flow model

This task aims to improve and enhance the accuracy of surface hydrological model discharge predictions, at both catchment and regional scales.

Project name -Title Project name or brief description of topic

Surface water flow model


The components

The surface water flow model framework in NZWaM-Hydro (NZWaM surface water model) is based on the TopNet national surface water model, developed by NIWA over the past 10 years. TopNet is used as a default model where more advanced surface water models are not available.

In this task, the surface water module will be coupled with a new water age model to identify the location and rate of water surface-groundwater interaction. The modules will be also be combined with the NZWaM groundwater module. These modules are designed to run on supercomputers at NIWA’s High Performance Computing Facility.

To develop the NZWaM surface water model, data from the hydro-geofabric task in this project, will be linked with our understanding of losing and gaining streams, and water-table fluctuation data from the underlying GNS Science and NIWA models.

The objective

This task aims to improve and enhance the accuracy of surface hydrological model discharge predictions, at both catchment and regional scales. This will require model development to further increase compatibility of surface water models with multi-source geospatial information, multi-source climate and weather information and multi-source surface water observations. To predict water transfer pathways, the surface water module will be combined with surface water age module, this will enable improved hydrological simulations of transport processes across landscapes.

This task also aims to improve process conceptualisation and the ability to simulate catchment-scale hydrological signatures such as water quantity, water age, land surface processes, surface water response to water use, land use and climate change.

The project is funded through the Strategic Science Investment Fund from the Ministry of Business, Innovation and Employment. 

Planned tasks for the year

  • Implement improved national soil and geological derived TopNet model parameters and model benchmarking.
  • Develop a realistic surface water take module within NZWaM-Hydrology-surface water model, and complete testing in one catchment
  • Benchmark internal and external post-processing of NZWaM-hydrology surface water model simulations to produce relevant outputs for NZWaM-hydrology end users. The functionality will focus on generating relevant hydrological flux information at relevant times and locations to facilitate use for our end users.  
  • Co-develop with NZWaM stakeholder reference group the characteristics of NZWaM-Hydro graphical user interface (HydroDesk NZ).

Progress to date

  • In collaboration with the benchmarking task within this project, implementation of modified digital river network - surface water process conceptualisation and parametrisation, updated soil and geological information in NZWaM-Hydro surface water module.
  • Conceptualisation of a three-tier catchment-scale surface water takes module based on existing information.
  • Ongoing discussions on a framework to couple surface water and groundwater, including the uncertainty of both components.

Outputs (if applicable) Papers published, web links, reports, etc.