Why falls were constructed on canals? Pakistan has world’s largest canal irrigation system. There are Five (5) rivers which make it Punjab. Punjab means five rivers (Indus, Chenab, Ravi, Satluj and Bias). From these 5 rivers many canals were digged and canals, distributors and water channels to irrigate punjab and sindh provice. On these canals Falls were established to speech up the water flow of the canals. These Falls are locally known as Jhaal, Chalaar or Thokar.