Place the cut rhubarb in a saucepan with the orange juice and water.
Bring to a slow boil over medium heat.
Simmer for 5 minutes, or until the Rhubarb is tender and breaking down.
Strain the liquid from the rhubarb using a sieve with a small weave (holes), retaining the liquid.
Place the rhubarb and blueberries back in the saucepan, along with 1/2 a cup of the retained liquid and the maple syrup.
Bring the mixture to a warm temperature over a medium heat.
Taste the mixture at this point and add more maple syrup if required.
Meanwhile, mix the arrowroot with 1/4 of a cup of the retained liquid. Whisk to ensure it is well combined.
Add the arrowroot liquid mixture to the saucepan and bring to the boil, stirring constantly.
Once boiling, continue to stir for another minute.
Place the mixture in the fridge to allow to cool and thicken.
Once completely cooled, pour into the cooled pie crust (there may be filling left over).
Place filled pie crust in the fridge for at least 2 hours.