Two persons were shot dead and a Dalit woman was injured on Thursday during a caste-clash over water sharing for irrigation in Bihar's Nawada district, police said.The incident in Khaira village, about 150 km from here, has caused tension in the area. Security forces have been deployed.The area is facing an acute shortage of rainfall. Farmers are restless for their kharif crop mainly paddy.Following a heated exchange between two groups earlier in the day, a powerful backward caste group opened fire and killed two persons on the spot while seriously injuring a Dalit woman, Akbarpur police Station Officer in-charge Sanjeev Mauaar said.She was admitted to a hospital in Nawada, he said.Bihar has recorded 22 per cent rainfall deficit during the 2018 monsoon.