Flooding wrecks water harvesting systems in Chimanimani

Participatory Organic Research Extension and Training (PORET) is member of PELUM Zimbabwe working in Chimanimani district, eastern Zimbabwe. PORET is working with communities to strengthen their capacity to design and set up water harvesting systems to sink water into the soil, replenish the watershed, regenerate the natural environment and increase crop yields. PORET hosts peer to peer trainings, facilitating demonstrations on dam construction and water harvesting. This was initiated in 2019 and the farmers took these skills to their villages, and as result there are many dams that farmers have constructed in their villages. Photo: PORET

Julius Piti, the Director of the Participatory Organic Research Extension Training (PORET) says the heavy rains experienced in January 2021 during the Tropical storm Eloise wrecked up nine of the 35 earth dams constructed at PORET’s agroecology centre in Chimanimani district, eastern Zimbabwe. The intricate water harvesting system has been under construction for the past one year.

The water harvesting system at PORET agroecology centre captures more than one million litres of water through earth dams, swells, water infiltration pits, gabions, cover crops, and diverse indigenous and exotic trees. The floods induced by tropical storm Eloise were more than the system had been designed to handle, resulting in the collapse of some dams and loss of harvested water. This is a critical learning point for PORET agroecology centre.

Julius says a technical glitch in the construction of the major dam’s spillway resulted in the collapse of the dam wall.

“The dams are designed with spillways that allow excess water to be channeled into other dams when the dam is full. The spill ways release the pressure from the dams to avoid breaking them. The massive water inflows was too much for our system. We now have to review and improve the construction process, “says Julius.

Constructing a water harvesting system calls for the ability to observe and understand what is happening on the land. The water harvesting system is then designed to minimize run off by sinking every rain drop into the ground. This is important especially in drought prone areas like Jinga village where PORET’s agroecology centre is located.

“I already have many ideas flooding my head about redesigning the dams. We will use gabions to strengthen the walls and we will increase the width of spillways to 5m or more. Going forward, the capacity of the water harvesting system needs to be broadened and strengthened as floods become the new normal,” says Julius.

The water harvesting system at PORET agroecology centre has transformed the ecosystem, creating a micro climate characterized by species diversity. Julius attributes this change to the work they are doing to slow down the flow of rain water so that it is kept within the PORET land for a longer time.

The annual rainfall received in Jinga village is less than 400mm. Rain water at the PORET agroecology training center is collected mainly through the roof as well as the surrounding mountains and directed into 35 earth dams. These earth dams play a significant role in raising the water table.