Use of vegetated agricultural drainage ditches to improve the ecological services of irrigation ecosystem

The aim of this study was to determine the role of riparian vegetation in the tertiary irrigation ditch to improve the quality of irrigation water based on water physics chemical parameters, community structure of benthic macroinvertebrates and biotic indices (the value of diversity index/H’ and Hilsenhof Biotic Index/HBI from benthic macroinvertebrates) as bioindicator of ecological services. The study was conducted by planting riparian vegetation in left and right side of ditch along the 270 m length and 0.7-1.0 m width in Kedung Pedaringan Village, Kepanj en District, Malang Regency, East Java Indonesia. Some hydromacrophytes species used to enriched existing riparian were Limnocharis flava, Ipomoea aquatica, Fimbristylis globulosa, Vetiveria zizanoides, Equisetum ramosissium, Typha angustifolia and Scirpus grossus. Monitoring of irrigation water quality (bicarbonate, dissolved oxygen/DO, total suspended solid/TSS, dissolved phosphates, total organic matter/TOM, total dissolved solid/TDS, total Kjeldahl nitrogen/TKN, total phosphates/TP, pH, conductivity, water temperature, nitrate, ammonium) and benthic macroinvertebrates community structure was performed at 30, 40 and 50 days after planting riparian vegetation. Monitoring was conducted in the area before planting riparian vegetation (upstream), midstream and downstream. Data identification and abundance of benthic macroinvertebrates at each location was used to calculate the value of H’ and HBI. Research results showed that after 30-50 days of planting, the enriched riparian increased its capacity to reduce significantly concentration of bicarbonate, TSS, TOM, dissolved phosphate, ammonium, and water temperature as well as to increase DO in irrigation water. The phytoremediation system slightly reduced TDS and concentration of total phosphates. Based on the index value can be concluded that the planting of riparian vegetation along the 275 m for 40 days is capable to improve the water quality from slightly contaminated to uncontaminated (based on H’) and from significant organic pollution becomes fairly significant organic pollution (based on HBI). It is concluded that enriched riparian vegetation increased significantly irrigation water quality and therefore it reduced organic pollution level.