Complex sentence: Hydroelectricity is generated from turbines in tunnel 1 through 3, while tunnels 4 and 5 were designed for irrigation use, although both tunnels are to be converted to hydropower tunnels to increase Tarbela's electricity generating capacity.
Split into simpler sentences: Hydroelectricity is generated from turbines in tunnel 1 through 3, while tunnels 4 and 5 were designed for irrigation use. Both tunnels are to be converted to hydropower tunnels to increase Tarbela's electricity-generating capacity.