A new technique to estimate net groundwater use across large irrigated areas by combining remote sensing and water balance approaches, Rechna Doab, Pakistan

Abstract

Over-exploitation of groundwater resources threatens the future of irrigated agriculture, especially in the arid and semi-arid regions of the world. In order to reverse this trend, and to ensure future food security, the achievement of sustainable groundwater use is ranking high on the agenda of water policy makers. Spatio-temporally distributed information on net groundwater use-i.e. the difference between tubewell withdrawals for irrigation and net recharge-is often unknown at the river basin scale. Conventionally, groundwater use is estimated from tubewell inventories or phreatic surface fluctuations. There are shortcomings related to the application of these approaches. An alternative methodology for computing the various water balance components of the unsaturated zone by using geo-information techniques is provided in this paper. With this approach, groundwater recharge will not be quantified explicitly, but is part of net groundwater use, and the spatial variation can be quantitatively described. Records of routine climatic data, canal discharges at major offtakes, phreatic surface depth fluctuations, and http://www.springerlink.com/media/99a0hcwgqn3rypqhlk1p/contributions/l/9/y/2/l9y25e2g0ghbm45j_html/fulltext.html (1 of 25)8-11-2005 9:37:32 10.1007/s10040-004-0394-5 simplified information on soil textural properties are required as input data into this new Geographic Information System and Remote Sensing tool. The Rechna Doab region (approximately 2.97 million ha), located in the Indus basin irrigation system of Pakistan, has been used as a case study. On an annual basis, an areal average net groundwater use of 82 mm year -1 was estimated. The current result deviates 65% from the specific yield method. The deviation from estimates using tubewell withdrawal related data is even higher.Keywords Remote sensing -GIS -Water balance -Groundwater management -Net groundwater use -Recharge -Irrigation management -Sustainability -Rechna Doab, PakistanResumen La sobre-explotación de recursos de agua subterránea amenaza el futuro de la agricultura de riego, especialmente en las regiones áridas y semi-áridas del mundo. Para revertir esta tendencia, y para garantizar seguridad alimentaria futura, la meta del uso sostenible del agua subterránea se encuentra alto en la agenda de los políticos. Información espacial y temporal en cuanto al uso neto de agua subterránea-i.e. la diferencia entre las extracciones de agua de pozos entubados para riego y recarga neta-se desconoce frecuentemente a la escala de cuenca hidrográfica. Generalmente, el uso de agua subterránea se estima a partir de inventarios de pozos o fluctuaciones de superficies freáticas. Existen deficiencias en relación con las aplicaciones de estos enfoques. En este artículo se aporta una metodología alternativa para calcular los diferentes componentes del balance hídrico de la zona no saturada utilizando técnicas geoinformativas. Aunque con este enfoque no se cuantifica de manera explícita la recarga de agua subterránea, la cual es parte del uso neto...

Basin-wide water accounting based on remote sensing data: an application for the Indus Basin

“…Data on withdrawals are normally obtained from tubewell density, electricity bills, farm interviews and changes in groundwater levels (e.g. Ahmad et al, 2005). This unfortunately does not provide a reliable and reproducible data set either.…”

“…This is an unfavorable situation that requires corrective action. For typical situations in irrigation systems, T is 67 % of the total ET (Ahmad et al, 2002). However, it is highly dependent on the pattern of rainfall.…”

Remote Sensing and Economic Indicators for Supporting Water Resources Management Decisions

“…The contribution to ET act from i rainfall can be estimated from the ET of a neighbouring rainfed pixel. The ET from irrigation must originate from groundwater in the absence of surface water and is a good indicator of net groundwater consumption in case no records are available (Ahmad et al 2005;Bastiaanssen and Hellegers 2007).…”

Groundwater surface water interactions and the role of phreatophytes in identifying recharge zones

“…Remote sensing software was used to digitize tree locations, and GIS tools were used to relate tree location with soil type, depth to water, and distance to rivers. While several studies used remote sensing approaches to investigate groundwater (Ahmad et al, 2005;Becker, 2006;Jiang et al, 2008;Münch and Conrad, 2007;Rodell et al, 2007), none specifically emphasized phreatophyte distribution. The specific need to incorporate groundwater root uptake with remote sensing techniques was articulated by Winsemius et al (2008).…”