The International Committee of the Red Cross said that every day, hundreds of gallons of wastewater are dumped into local waterways that trickle through urban areas in Gaza.
Failing wastewater treatment networks in the region increase the risk of waterborne parasites that threaten the health of the local community.
The ICRC said Israeli restrictions on the import of construction materials were eased last year, though spare parts and raw materials are at a premium.
"It's a great challenge to carry out construction projects in the Gaza Strip, as building materials cannot be imported," said Marco Albertini, an ICRC engineer working in the area, in a statement.
The Red Cross called on governments and other interested parties to make sure those living in conflict zones like Gaza have access to clean water and basic sanitation.
"The water and sanitation infrastructure in Gaza is in dire need of a comprehensive upgrade," added Albertini.