Practice note: Selecting climate data

Practice note: Selecting climate data

This practice note is one of a set developed to provide consistency and transparency of river system models being used within the Murray-Darling Basin. The notes cover modelling practices, such as naming conventions for folder structures, to model methods, such as for flow routing and residual inflow estimation, and have been developed through a collaboration between the MDBA, Basin States and CSIRO.

Produced in collaboration with:

This practice note, Selecting climate data, describes the recommended conventions for sourcing and quality assuring climate (rainfall and evaporation) data for Source river system models that underpin water resource plans; and provides examples of different sources and practices used by jurisdictions.

Background

Climate data is key input to any river system model. The use of the same data source for climate data across models allows model users to more easily understand the model input data.

Scope

• This practice note covers the different climate data sources and QA checks used by the different jurisdictions in the MDB.

General principles

For rainfall

• use observed data and infill missing rainfall data using equivalent SILO patched point data - https://www.longpaddock.qld.gov.au/silo/
• use Bureau of Meteorology (BoM) rainfall gauges (in preference to patched point data) if there is insufficient station coverage using patched point data and BOM gauges provide better quality data. When using BOM data:
  • ensure that gauges have a reasonably long period of observed data
  • manually infill missing data.

For open water evaporation

• use Patched Point Morton Lake evapotranspiration

For crop modelling and Urban Demand modelling

• use Patched Point FAO56 evapotranspiration data

For rainfall runoff modelling

• use Patched Point Morton's Wet
• where possible, use sites where the variables used to calculate evapotranspiration are available

Appropriate QA checks should be undertaken.

Future extensions to climate data sets should be done by appending the new climate data to existing data sets, rather than replacing the whole data set.

Where climate data is used in the model

Suggested quality assurance checks

Rainfall

• Visually inspect daily time series to check for obvious errors
• Test the data for trending/non stationarity. If a trend is identified in the raw data or the infilled data it should be investigated
• Calculate the mean annual rainfalls for each infilled data set and view cumulative and residual mass curves to check the data
• Use gridded data as a cross-check of spatial variability and possibly also to calculate mean catchment data.   In some areas, gridded data may not be appropriate to use directly in the model, due to spatial variation, station density, and rainfall surface interpolation.
• Use a double mass curve with district rainfall gauge to identify trends – otherwise use trend statistics
• Check for gaps and cumulative totals
• For rainfall runoff modelling: check the selected rainfall sites against gauged flow data e.g. average annual rainfall-runoff ratios at major gauges to assess whether there are any mass balance anomalies or else undertake preliminary rainfall-runoff modelling to determine if the runoff characteristics fall within expected limits.

Evapotranspiration

• Give preference to stations with the longest recording of sunshine hours and cloud data as these are used in the calculation of Morton and FAO56 methods
• Consider site characteristics when assessing the representativeness of the site for the catchment/valley e.g. elevation, distance from coast
• Comparing pan data and Morton's data (eg means) may be useful to ensure that they are in expected range.

References

McMahon TA, MC Peel, L Lowe, R Srikanthan, TR McVicar (2013) Estimating actual, potential, reference crop and pan evaporation using standard meteorological data: a pragmatic synthesis. Hydrol. Earth Sci., 17 1331-1363

Links to relevant sections of the eWater website

• /wiki/spaces/SC/pages/52196842
• /wiki/spaces/SC/pages/51643415
• /wiki/spaces/SC/pages/52196829
• Data preparation
• Climate data import tool