Appraising a Watershed Before Extending Eucalyptus and Drilling Thirty Borewells

The spatial pattern is suggestive but not conclusive. A 14-16 m depth in the eucalyptus block against 7-9 m on the opposite side shows a local, not watershed-wide, drawdown - consistent with tree water use, but equally consistent with a cluster of new borewells on that side. Check dams raise recharge and cannot themselves lower a water table; they can, however, mask a decline elsewhere. Before blaming Eucalyptus tereticornis, obtain: the number and horsepower-hours of borewells commissioned on each side since 2015, since 30 additional wells would explain the difference with no role for the trees; pre-monsoon hydrographs from a dedicated observation well in each zone rather than farmers' wells, which are pumped and therefore biased; and a water balance comparing 20 ha of eucalyptus at roughly 1,100 mm/year transpiration with the estimated recharge from 14 check dams. The defensible conclusion at this stage is a joint cause, not a verdict - and the committee should be told that neither 'the trees dried the wells' nor 'the check dams failed' can be established from the present record.

Load = 140 kg N/ha x 45 ha = 6,300 kg N/year as urea. Paddy typically loses 30-50% of applied N through volatilisation, denitrification and leaching, so 2,000-3,000 kg N/year is mobilised; spread over 250 ha that is 8-12 kg N/ha/year, which is enough to raise shallow groundwater nitrate over a decade. Paddy on the valley floor is hydraulically connected to the shallow aquifer, so the pathway is plausible. But a rise to 62 mg/L is steep for that load, so first check whether the sampled wells are shallow and close to the command, whether samples were filtered and preserved, and whether septic tanks or cattle sheds sit nearby - these are common confounders in a village cluster. Monitoring: 15 georeferenced wells sampled quarterly for NO3-N, NH4-N and EC, plus suction lysimeters in the paddy. Agronomy: leaf colour chart-based urea in three splits, green manure or azolla, and a 25% cut in the first year with yield monitoring. Denitrification in the saturated valley floor is a genuine sink, so record the water table alongside the N rate.

Do not release funds for the 40 ha extension and 30 borewells as proposed. The eucalyptus economics are thin - 1.8 t/ha x Rs 4,500/t = Rs 8,100/ha over six years, under Rs 1,400/ha/year gross - while the 25-30% sorghum loss within 10 m is an uncompensated cost borne by the same farmer, and the well data are unresolved. Counter-proposal: (i) restrict new planting to degraded uplands and single boundary rows, keeping the crop interface clear and installing a root barrier or annual root pruning where trees border sorghum; (ii) substitute part of the area with a nitrogen-fixing, water-conserving species (Leucaena, Sesbania) or a fruit tree such as ber on the uplands, which yields fodder or fruit and softens the crop trade-off; (iii) make every new borewell conditional on entry in a groundwater register and an associated recharge structure; (iv) pay the affected farmers for tree-crop interface loss through a watershed benefit-sharing arrangement. Monitoring condition: measure sorghum yield at 0-5 m, 5-10 m and beyond 10 m from the tree line for two seasons, and hold the extension decision until those data and the observation-well hydrographs are in hand.