Validation of the new B2B Bankless Channel Irrigation System model Michael Grabham, R. Soppe, J. Hornbuckle, R. Smith and S. Raine

Outline System overview Hydraulic challenges B2B model Bay-scale comparison Whole field simulations Conclusions

System Overview

System overview

System overview

Why the system is being considered Advantages Labour savings Can be automated Machine efficiency Expanded cropping options

Hydraulic challenges

Hydraulic challenges Variable inflow rates Variable bay sizes Bay to bay hydraulic interaction

Hydraulic challenges Variable inflow rates Volume balance approach used to determine surface storage and infiltrated volume Variable discharge complicates calculations

Hydraulic challenges Flow rate Time

Hydraulic challenges Variable bay sizes 60:100:40 bay ratios Surface storage volume accumulation Interconnecting pipe size selection Drainage water minimisation

Hydraulic challenges

Hydraulic challenges

Hydraulic challenges Bay to bay hydraulic interaction Calculate the available volumes Calculate inflow rates Select adequate bay dimensions Select adequate pipe sizes

B2B model

B2B model Current simulation models Single dimension Variable inflow Recession phase limitations Assume free flowing drainage

B2B model Clemmens’ (2007) surface irrigation design approach Volume balance principles Spreadsheet based Simultaneously solves for advance and inlet depth Uses fixed inflow

B2B model Darcy Weisbach equation

Darcy Weisbach equation B2B model Clemmens’ Approach Darcy Weisbach equation

B2B model Model features Infiltration parameters Bay or furrow inflow rates Manning n selection σy pre-defined Level furrow or bankless accommodated Target infiltration depth Up to nine bays can be simulated Several irrigation termination options Completion of advance After set delay After target infiltration depth achieved

Bay scale comparison

B2B – Bay Scale Discharge Errors from Measured winSRFR = 65% SISCO = 65% B2B = 18%

B2B – Bay Scale Advance and recession

B2B – Bay Scale Infiltrated depth

B2B – Bay Scale Simulation discrepancies Attributed to model assumptions Level water surface Friction ignored Infiltration during recession

Field simulations

B2B – Field Scale Advance and recession Bay 1 Bay 3 Bay 2

B2B – Field Scale Depth

B2B – Field Scale Inlet hydrographs

B2B – Field Scale Inlet cumulative hydrographs

Conclusions Novel approach taking into account bay-to-bay interaction Enables simulation of multiple bay systems Discrepancies with known causes

Acknowledgements CRC IF Postgraduate scholarship IAL and CRC IF Travel Fund grant CSIRO Land and Water, Griffith USQ, Toowoomba

Acknowledgements