Study Results

The Ouardanine Perimeter is irrigated by recycled water from the Ouardanine WWTP, which is located 2 km north of Ouardanine town in the Monastir Governorate. Wastewater collections come from predominantly domestic sources in the town, although some wastewater comes from industrial sources, for example, car washes and slaughterhouses. The Ouardanine WWTP was built with a design flow of 1,500 m3 /day, which is expected to be increased to 2,900 m3 / day when the current extension project is completed. Wastewater is treated at a secondary level by a medium-load activated sludge treatment system at the plant and then conveyed to the Oued El Guelta wadi upstream of the Ouardanine Perimeter (Figure 4.2) by means of: A storage basin with a capacity of 1,000 m3 that is located near the Ouardanine WWTP’s discharge point into the El Guelta wadi. A filtration plant consisting of two gravel filters, two screen filters and two disc filters. A pumping station with a suction tank equipped with three 20 L/s pumps of 40 m in height, one of which is an emergency pump. A 2.4 km long DN250 asbestos cement delivery pipe. A semi-underground reinforced concrete regulation tank with a capacity of 500 m3 is located at the head of the perimeter. A buried piping distribution network fed by gravity from the regulation tank equipped with 22 irrigation hydrants. The irrigation hydrants are reinforced concrete manholes with tamper-proof closures and equipped with valves and a meter, although it is noted that these meters are generally out of order. The payment of volumes used by each farmer is made on a flat rate basis in relation to the irrigated area. A common fee is applied corresponding to an annual amount of USD 99/ha/year/farmer. Plot networks with buried PVC pipes installed by farmers. The irrigation techniques used are localized for arboriculture while sprinkler irrigation is used for forage crops. The creation of the Ouardanine Perimeter has resulted in significant socio-economic, health and environmental benefits. Economic benefits include an increase in the value of agricultural land. The price of an irrigated hectare increased from USD 1,800 in 1996 to USD 1,364 in 2014. It is currently valued at USD 7,182. There has also been an increase in the agricultural production of the irrigated farms, which represents triple the average recorded in the whole of the Republic of Tunisia including: 25 ha of peach trees with an average production of 30 tons/ha. 10 ha of fig trees with an average production of 10 tons/ha. 15 ha of pomegranate trees with an average production of 40 tons/ha. 24 ha of olive trees intercropped with various fruit trees. Jobs have also been created for young people in the project area as the number of working days has increased from 20 days/ha in 1996 to 155 days/ha just four years after the perimeter was irrigated. Environmental benefits include minimizing the discharge of recycled water from Ouardanine WWTP into the El Guelta wadi. In 2019, between March to September, all of the recycled water was used within the perimeter as a result of a significant lowering of the water table, which is an ongoing challenge. This enabled the return of agricultural activity on 7.2 km of land located near the wadi that had been previously damaged because of discharge (Image 4.1). Other benefits include the use of treatment sludge from the plant as an organic fertilizer. The Ouardanine Perimeter also plays an important role in raising awareness of irrigation by recycled water from wastewater treatment plants at the local as well as national levels. It receives an average of 1,000 visitors each year. The Ouardanine Perimeter is located in an extensive agricultural area where both arboriculture (especially dryfarmed olive trees) and cattle rearing (without a grazing area owing to the absence of irrigation and fodder production) play an important role in generating income for the population. The absence of other sources of conventional water and the aridity of the climate makes the possibility of extending the irrigated area highly probable, particularly given the demands made by a large proportion of the farmers in the area who deem it necessary.