It was hypothesized that provision of subsurface drainage and cycles of monsoonal rains facilitated use of higher salinity waters   in irrigation without affecting crop production.

 

Reclamation of waterlogged saline lands generates large quantities of saline effluents, which have to be suitably disposed. Reuse of these waters offers opportunity to augment limited fresh water supplies for irrigation and reduce disposal volumes. The three important techniques of abstraction of salty waters include horizontal drainage in high water table areas, skimming wells in situations where marginal quality water floats over higher salinity water and shallow tube wells in low table conditions could helped ameliorating water logging and salinity and was providing.  Several variants of drainage and reuse have been practiced in Northwest India.  Based on a   number of studies, a model for soil salinization and desalinization in monsoon climate was conceptualized and the results of field studies were used to validate the hypothesis. The important outputs, which are summarized , provide  the  scientific basis of  increased crop productivity, water use efficiency and farm income; resulting from physical and biological interventions as moderated by monsoon rains and drainage.

Monsoon climate enabled use of relatively higher salinity waters as it set in an annual cycle of soil salinization (during winter and summer) and desalinization (during monsoon season). Major use of saline waters occurred during winter season when the evaporative demands were low and salts in the soil profile had been leached.

Subsurface drainage system   enabled use of higher salinity waters and for the given salinity of applied water, it improved crop yield by 10-15 % as compared to normal situation The quality of drainage effluents extracted through horizontal subsurface drainage system (SSDS)  generally improved with the passage of time, whereas it declined in case of skimming wells

 Water reuse reduced drainage water disposal requirement on an increasing scale with passage of time and helped maintaining better water quality in rivers and stream during non-monsoon periods (Conjunctive use even with very limited canal water (fresh water) availability vastly improved the crop water use efficiency and profitability and afforded larger area under irrigation.

The guidelines for practicing conjunctive use of sodic and fresh waters have been prepared and would be useful to irrigators in practicing irrigation with these waters

Salt tolerant varieties of different crops like rice, wheat and mustard etc, are available.  Taking advantage of the synergy between plant salt tolerance and chemical and physical interventions (chemicals like gypsum and drainage for water table control etc), it was possible to use waters salinity higher than hitherto prescribed

The final output was the modified guidelines which can be easily followed by irrigators without inviting significant adverse impact on land and water.

 

The findings described herein are based on analytical analysis and multi-location testing over a period of time and therefore have high reliability. Information generated has been very useful to state development agencies in formulating policies for allowing disposal of drainage effluents.