Improper on-farm irrigation management practices lead to poor water distribution, non-uniform crop growth, excessive leaching in some areas (leading to water logging), and insufficient leaching in others (leading to salinity buildup), all of which decrease the yield per unit of land area and per unit of water applied. But improvement in irrigation practices lead to more uniform water distribution, minimize water application, irrigation costs, nutrient leaching, and result in economic viability of irrigated agriculture. So priority should be given for proper design and management of irrigation systems and improved irrigation practices to fully exploit the irrigation schemes. Hence, the objective of the study was to improve water and crop productivity of onion and potato through the use of wetting front detectors by water user association at Koga scheme. In Koga irrigation scheme, there are 11 night storage, which irrigate 12 blocks (7000 ha). From those three blocks were selected. Namely: Tagel, Adibera and Chihona blocks. From each block two water user associations (WUA) have been selected and training on how to use the WFD was given: one WUA grew onion while another one cultivated potato. For onion 2.04 ha of land were managed by 9 WFD and 0.82ha were managed by farmer‟s own irrigation system. For potato 1.68 ha of land were managed by 10 WFD and 0. 42 ha of land were managed by farmers own irrigation system. In this study a total of 43 farmers irrigated using WFD while 13 farmers were irrigating based on their traditional knowledge. During installation the furrow length for onion was 5m and for potato 20m. The WFD was placed at ¾ of the furrow length from the entrance of the furrow. The shallow detector installed at 1/3 of the root zone (20 cm in this case) and the deep detector installed at 2/3 of the root zone (40 cm). Potato fields that were irrigated based on WFD response received on average 43% less water compared to control fields (i.e. 431mm instead of 753mm) (p<0.05). This resulted in a significant yield increase of 6 % (p<0.05) in the WFD plots. Similarly, for onion a reduction in irrigation depth of 25% was obtained when farmers were guided by WFD (i.e. 504 mm instead of 676mm (p<0.05). While yield increased in the WFD fields by 5%, this was not significant. At scheme level, if all fields were onion guided by WFD, 1509 ha additional could be irrigated. Similarly if all fields were potato guided by WFD, additional land to be irrigated could be 2966 ha. This study has shown that available water in dams can irrigate more land by using on farm water management technologies.