| Term No. | Term Name | Term Description |
| 1628 | R horizon | A layer of continuous indurated rock, sufficiently cohesive when moistened as to make hand digging with a spade impracticable...... |
| 3178 | Rabi and monsoon sections of a canal | These terms are used in Indian sub-continent. The `rabi section` is the cross-sectional area of a canal in which assured supply is available for matur..... |
| 3985 | Rabi crop (Bangladesh, India and Pakistan) | Winter crop...... |
| 2692 | Race | The channel that leads water to or from a water wheel or water turbine such as head race or tail race...... |
| 6317 | Radar | Process or equipment that uses the reflection of beamed, repeated and timed electromagnetic-magnetic radiation to detect, locate and / or quantify obj..... |
| 5347 | Radial drainage pattern | Drainage pattern resembling the spokes of a wheel in which drainage channels flow radially either outward from a peak or inward toward a basin...... |
| 5431 | Radial flow pump | A centrifugal type pump in which the pressure for the circulating water is developed principally by action of centrifugal force...... |
| 3930 | Radial flow turbine | A type of turbine in which the path of any particle of water in its flow through the runner lies substantially in a plane perpendicular to the axis of..... |
| 2933 | Radial gate, or Tainter gate | A gate that may be pivoted or hinged with a water face that is usually arc with the centre of curvature at the pivot and water load is transferred thr..... |
| 2972 | Radial lock gates | A radial gate used in a lock. It is required to be raised high enough to provide necessary clearance to the passing traffic...... |
| 4184 | Radial well, Ranney well, or Collector well | A variation of strainer well; in this case the strainers are driven horizontally in the water-bearing strata, radiating from a central sump or open we..... |
| 4517 | Radial-flow pump | A pump in which fluid enters the rotating impeller near the axis of rotation and discharges with a combined radial and tangential motion...... |
| 3579 | Radial-gate spillway | Overflow spillway utilizing radial gates; when automatic, will automatically open or close with the rise or fall of the water surface in the canal...... |
| 7230 | Radioactive decay | Disintegration of the nucleus of unstable nuclides by spontaneous emission of charged particles and/or photons...... |
| 6262 | Radioactive tracer | Material detectable by its emitted ionizing radiation and suitable for water tracing even at very low concentrations...... |
| 7238 | Radioactive tracer | Radioactive material detectable by its nuclear radiation; useful for tracing sources of water, even at very low concentrations. ..... |
| 7239 | Radioactive waste | Any waste that contains radioactive material; especially in concentrations that exceed amounts allowed by law. ..... |
| 7226 | Radioecology | The study of the effects of radiation on plants and animals in natural communities...... |
| 7227 | Radioisotopes | Radioactive forms of chemical compounds...... |
| 7229 | Radionuclides | Any nuclide that emits radiation...... |
| 4218 | Radius of a well | The radius of the inside of the well casing or screen, or the radius of the bore hole for an uncased well (illustrated)...... |
| 4239 | Radius of influence | The radius of the circle of influence (illustrated)...... |
| 3853 | Raft foundation | A layer of concrete, usually reinforced, extending under the whole area of columns, piers and abutments and projecting outside their base periphery; u..... |
| 4681 | Railing | Agricultural method of brush removal from a field using a tractor-drawn railway rail...... |
| 773 | Rain | Precipitation in the form of liquid water drops greater than 0.5 mm...... |
