79 Original scientific paper Received: October 04, 2017 Accepted: December 14, 2017 DOI: 10.2478/rmzmag-2018-0008 SaltMod estimation of root-zone salinity Varadarajan and Purandara Application of SaltMod to estimate root-zone salinity in a command area Uporaba modela SaltMod za oceno slanosti koreninske cone na namakalnih površinah Varadarajan, N.*, Purandara, B.K. National Institute of Hydrology, Visvesvarayanagar, Belgaum 590019, Karnataka, India * [email protected] Abstract Povzetek Waterlogging and salinity are the common features - associated with many of the irrigation commands of - Poplavljanje in slanost tal sta običajna pojava v mno surface water projects. This study aims to estimate the vljanju slanosti v koreninski coni na levem in desnem gih namakalnih projektih. V študiji poročamo o ugota root zone salinity of the left and right bank canal com- mands of Ghataprabha irrigation command, Karnataka, - obrežju kanala namakalnega območja Ghataprabhaza India. The hydro-salinity model SaltMod was applied delom SaltMod so uporabili na izbranih kmetijskih v Karnataki, v Indiji. Postopek določanja slanosti z mo to selected agriculture plots at Gokak, Mudhol, Bili- parcelah v okrajih Gokak, Mudhol, Biligi in Bagalkot gi and Bagalkot taluks for the prediction of root-zone - salinity and leaching efficiency. The model simulated vodnjavanja tal. V raziskavi so modelirali slanost v tal- za oceno slanosti koreninske cone in učinkovitosti od the soil-profile salinity for 20 years with and without nem profilu v razdobju 20 let ob prisotnosti podpovr- subsurface drainage. The salinity level shows a decline šinskega odvodnjavanja in brez njega. Slanost upada with an increase of leaching efficiency. The leaching efficiency of 0.2 shows the best match with the actu- vzporedno z naraščanjem učinkovitosti odvodnjavanja. al efficiency under adequate drainage conditions. The Učinkovitost 0,2 najbolje ustreza dejanski učinkovitosti model shows a steady increase, reaching the levels up v ustreznih pogojih odvodnjavanja. Model kaže stalno to 8.0 decisiemens/metre (dS/m) to 10.6 dS/m at the koncu 20-letnega obdobja v pogojih brez odvodnjava- naraščanje do ravni 8,0 - 10,6 deci Siemens/meter na end of the 20-year period under no drainage. If suitable drainage system is not provided, the area will further - nja. Če ni na voljo primernega sistema odvodnjavanja, get salinised, thus making the land uncultivable. We stane zemlja neprimerna za obdelovanje. Iz opravljene se naraščanje slanosti v območju nadaljuje, tako da po conclude from the present study that it is necessary to provide proper drainage facilities to control the salinity zagotoviti ustrezno odvodnjavanje, da se zaustavi na- študije sledi, da je potrebno na proučevnem območju levels in the study area. raščanje slanosti. Key words: waterlogging, SaltMod, root-zone salinity, Ključne besede: poplavljanje tal, SaltMod, slanost leaching efficiency, artificial drainage odvodnjavanje v koreninski coni, učinkovitost odvodnjevanja, umetno Open Access. © 2018 Varadarajan, N., Purandara, B.K., published by Sciendo. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. 80 Introduction Sensing Directorate of the Central Water Com- mission (New Delhi, India) carried out a study Waterlogging is said to occur when the water of Ghataprabha Command Area using remote table rises to within the root zone of crops. Cli- sensing and GIS [5] and delineated the water- mate, topography and geology play a dominant logged and salt-affected areas in the command. role in governing the occurrence, movement Hiremath [6] carried out a study on waterlog- and storage of water. Any change in the water ging and salinity, as well as the impact of ma- balance of an area causes a change in water ta- jor irrigation projects on agriculture land and ble, leading to either waterlogging conditions the reclamation of affected areas in Bagalkot or depletion of water table depending upon the and Biligi taluks of the Ghataprabha Command nature of the change. Rise or decline in the wa- Area. Varadarajan et al. [7] highlighted the sta- ter table is not desirable because both the phe- tus of salinity in the aquifers of the Ghataprabha nomena degrade the sub-surface environment, Command Area due to a combination of various thereby degrading the ground water regime [1]. hydro-geochemical processes contributed by Direct evaporation of ground water from the increase in mineralised water, rock weathering capillary fringe leads to salinisation of the soil, and agricultural activities. and in advanced stages, to the salinisation of Bahceci et al. [8] simulated the effect of differ- ground water as well. Lack of aeration in the ent drain depths on the amount of drainage root zone, coupled with soil salinity, adversely water, root zone salinity and depth of water affect crop yields in waterlogged areas. Seepage table in the Konya–Çumra Plain, Turkey, by us- losses occurring along the routes used for the ing SaltMod. Simulation results indicated that transfer of water from available resources has the leaching efficiency is 0.7 and the natural caused waterlogging and development of sa- drainage is 0.120 m/year in the test area. Khan linity in many irrigation commands. It is a fact et al. [9] used SaltMod for suggesting remedi- that in some of the major projects, irrigation is al measures to the highly salt-affected areas. in vogue for >3 decades, and the abacus have The predicted values showed very good cor- been stabilised with the farmers enjoying all relation with the observed conditions, there- the benefits, including access to uncontrolled by indicating the applicability of SaltMod as a use of surface water through the canals in the management tool. Hebsur [10] made detailed case of those in the upper and middle reaches ground-water quality studies in the Malapra- of the projects [2]. With the availability of sur- bha and Ghataprabha canal command areas us- face water throughout the year, farmers found it ing SaltMod, and the model predicted that there rarely necessary to use the ground water, with is a decrease in the root-zone salinity as the ir- the result that ground water utilisation became rigation with good-quality water increased in almost negligible. The net result was a rise in combination with poor-quality waters. Shrivas- ground water levels, gradually building up the tava et al. [11] applied SaltMod for the Segwa water table, giving rise to waterlogging con- minor canal command. The model predicted ditions. In addition, waterlogging also results fairly accurate trends in the region and it was in the accumulation of salt in the top soil or found that SaltMod is an effective tool to fore- ground surface, rendering it infertile. cast various situations once the model is cali- Purandara et al. [3] carried out a study on the brated and validated for use in a given agro-cli- waterlogging problems in the canal commands matic situation. Poornima et al. [12] estimated of the hard rock region of the Ghataprabha the root-zone salinity of salt-affected areas of command and highlighted the problems of wa- some parts of Gokak and Ramdurg taluks of terlogging and salinity in the command area. Belgaum District and Mudhol Taluk of Bagalkot Dilip et al. [4] analysed the ground water char- District, Karnataka, India, using SaltMod. The acteristics of the Ghataprabha command under model simulated the soil-profile salinity for a geographic information system (GIS) environ- 20 years under different conditions, viz. with ment and reported the acute problem of ground and without sub-surface drainage. The salinity water salinity. National Institute of Hydrology level shows a decline with an increase of leach- (Roorkee, Uttarakhand, India) and the Remote ing efficiency. This study aims to estimate the RMZ – M&G | 2018 | Vol. 65 | pp. 079–088 Varadarajan, N., Purandara, B.K. 81 Figure 1: Index map of the study area. root-zone salinity and leaching efficiency of The proposed right bank canal is expected to the salt-affected areas of the left and right bank irrigate an area of about 155000 ha. canal commands of Gokak, Mudhol, Biligi and The topography of the area is undulating with Bagalkot taluks of Ghataprabha irrigation com- table lands and hillocks typical of the Deccan mand. The hydro-salinity model ‘SaltMod’ was Traps. General topographic elevation varies applied for this study area, which computes the between 500 and 900 m above mean sea level salt and water balance for the root zone, transi- with a gradual fall from the West towards the tion zone and aquifer zone. - The command area of Ghataprabha reservoir is ers Krishna and Ghataprabha follows the GLBC - upEast. to TheBiligi. catchment The command boundary area between essentially the rivlies within the Krishna river basin and is drained by longitudes,located between covering 16°0′8″N an area and of 16°48′9″N317430 ha lati di- the Ghataprabha River. The Ghataprabha River videdtudes andbetween between the 74°26′43″E Belgaum and and Bijapur 75°56′33″E dis- is one of the right bank tributaries of the river tricts of Karnataka. The index map of the study Krishna in its upper reaches. The river origi- area is shown in Figure 1. The study area is nates from the Western Ghats in Maharashtra bound by the Krishna River in the north, Ma- at an altitude of 884 m and flows westwards for harashtra state to the west, the confluence of about 60 km through the Ratnagiri and Kolha- Krishna River and Malaprabha River in the east pur districts of Maharashtra. In Karnataka, the and the basin boundary between the Ghatapra- river flows for about 216 km through Belgaum bha and Malaprabha rivers in the south. The ex- District. isting canal command area (net command area The command area falls in the semi-arid zone is 161871 ha) is served by the Ghataprabha Left and falls under drought-hit areas.