Here, a relatively low variation in water level would indicate {HEAD ~ the presence} of {TAIL ~ a siphonic phenomemon} 
Here , a relatively low variation in water level would indicate { HEAD ~ the presence } of { TAIL ~ a siphonic phenomemon }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL