Groundwater and soil salinity variations in a canal command area in Pakistan

Abstract

This three-year study was undertaken to investigate the groundwater and soil salinity variation in a canal-irrigated area. Water and soil samples were collected along 54 tertiary canals located on six secondary canals (two each at head, middle and tail end) of a main canal. Data of crop yield and income of the farmers were also collected. The results show that electrical conductivity (EC) of groundwater increased from head to lower reaches along all the irrigation channels, i.e. main, the secondary and the tertiary canals. Similarly, the soil water EC e also increased with increased distance from the head of the irrigation system. Reduced canal water supply at lower reaches of the irrigation system forced the downstream water users to pump more groundwater, thereby increasing their irrigation cost. The deteriorating groundwater quality further adds misery to the downstream farmers by degrading productivity of their lands caused by excessive use of saline groundwater. Location of the water users along the canal irrigation system had an impact on their crop yield as well as income and these parameters decreased with increased distance from the head of the irrigation channels. For example, the net income of the tail-end farmers varied from 43% to 59% of the head-end farmers. Copyright # 2008 John Wiley & Sons, Ltd. RÉ SUMÉ Cette étude de trois ans a été entreprise pour étudier la variation de la salinité des eaux souterraines et de l'eau dans le sol dans un périmètre irrigué par des canaux. Des échantillons d'eau et de sol ont été prélevés le long de 54 canaux tertiaires situés sur six canaux secondaires (2 en tête, au milieu et en extrémité) d'un canal principal. Des données sur le rendement et le revenu des fermiers ont été également rassemblées. Les résultats montrent que la conductivité électrique des eaux souterraines a augmenté de l'amont vers l'aval le long de tous les canaux, principal, secondaires et tertiaires. De même la conductivité électrique de l'eau dans le sol a augmenté avec la distance à la tête du système d'irrigation. Une alimentation en eau réduite en extrémité de canaux oblige les utilisateurs aval à pomper plus d'eaux souterraines augmentant de ce fait leur coût d'irrigation. La mauvaise qualité des eaux souterraines augmente la misère des fermiers aval en dégradant la productivité de leurs terres par suite d'une utilisation excessive des eaux souterraines salines. La localisation des utilisateurs le long du système d'irrigation a eu un impact sur leur rendement et sur leur revenu; ces paramètres ont diminué avec la distance à la tête du système d'irrigation. Par exemple, le revenu net des fermiers de l'extrémité aval a diminué de 43% à 59% par rapport à celui des fermiers de l'amont.

Command-scale integrated water management in response to spatial climate variability in Lower Bari Doab Canal irrigation system

“…Similarly, Qureshi & Akhtar (2003) point out that the cost of installing tubewell in areas where water table depth is more than 24 m is 7 times higher than those areas where water table depth is around 6 m. Owing to such extraordinary cost differences regarding groundwater pumping, farmers suffer to different extents, depending upon the location (whether at head/middle/tail) of the main canal and/or watercourse. The fact that farmers located at the upper reaches of the irrigation canals get higher income and that income progressively decreases downstream along all main, secondary and tertiary irrigation canals has also been highlighted by Latif (2007) and Latif & Ahmad (2009). The difference in income was attributed to larger use of groundwater towards the tail reaches of the irrigation channels, incurring higher costs to the farmers.…”

Improving Water Management in Pakistan Using Social-Ecological Systems Research

“…While surface water allocations are regulated by provincial governments, local power dynamics often mean that wealthier farmers living near the head of distributaries have greater access to surface water supplies, with many distributaries running dry at the tail-end, especially in southern Punjab and across the Indus delta areas of Sindh (personal observations -see, for example Mitchell et al [2020] -though Shah et al's [2016 efforts to validate such observations with analysed data paint a more complex picture; also see Anwar and Ul Haq [2013] for an analysis of inequity along the length of a canal). The resulting increased dependency on groundwater at tail-ends inflicts a greater cost burden on farmers, increases rates of depletion, and results in groundwater of decreasing quality being used, with associated salinisation and lower productivity of the land for these farmers (Latif 2007;Latif and Ahmad 2009;Basharat 2012;Punthakey et al 2015). Variations in access to both surface and groundwater feed a vicious cycle that exacerbates existing inequalities.…”

Groundwater modelling for need assessment of command scale conjunctive water use for addressing the exacerbating irrigation cost inequities in LBDC irrigation system, Punjab, Pakistan

“…Similarly, Qureshi and Akhtar (2003) point out that the cost of installing tubewell in areas where watertable depth is more than 24 m is seven times higher as compared to those areas where watertable depth is around 6 m. Due to such extra ordinary cost differences regarding groundwater pumping, farmers suffer to different extents, depending upon their location (whether at head/middle/tail) of the main canal and/or watercourse. The fact that farmers located at upper reaches of the irrigation canals get higher income and it progressively decreases downstream along all main, secondary and tertiary irrigation canals has also been highlighted by Latif (2007) and Latif and Ahmad (2009). According to Hussain (2005), tail-end farmers, often the poorest, suffer a twin disadvantage-less water and more uncertainty.…”