A forage chopper machine was developed for compressing and chopping freshly collected water hyacinth in order to facilitate handling and transportation from water bodies to the utilization factories. The machine developments have been proposed as means of reducing volume and biomass or increasing density of the aquatic weeds that having large quantity of volume and moisture content. Whereas, the feeding mechanism of the chopper was modified and adapted for compressing process using three modified drums, controllable compressing loads, and a rough surface flat belt. The performance of the developed chopper was tested for volume and biomass reduction under three processing variables such as four feed rate levels (8, 12, 16, and 20kg/min), four appliedcompressing load levels (2, 3, 4, and 5kN), and four cutting knife speeds levels (3, 4.5, 6, and 7.5m/s). The developed chopper performance was evaluated firstly by determining changes in specific mass, volume, and chopping efficiency as affected by the processing variables. Secondary by determining machine productivity (ton/h), specific energy required (W.h/t) to operate the developed chopper and machinery unit cost (LE/ton). The obtained results revealed that the developed chopper reduced the specific volume and mass of fresh water hyacinth up to 74.6% and 26.3% at a feed rate of 20 and 8kg/min respectively, knife speed of 6m/s and applied compressing load of 5kN. To run the machine at the highest processing variable levels, maximum chopping efficiency of 80% and machine productivity of 0.97ton/h were achieved. The maximum power and specific energy were required to operate the chopper of 3.9kW and 12.5kW.h/t at a feed rate of 20 and 8kg/min,respectively and applied compressing load of 5kNwith lower machineunit cost of about9.5LE/ton.