As climatic change and land use are altering the hydrographic regime, most catchments are progressively becoming drier and farmers are shifting from rainfed agriculture to irrigation practices to enable them to carry out income-generating activities throughout the year. The Ghanaian government has recently been promoting irrigation agricultural practices as the population keeps increasing and the demand for food keeps soaring. In order to keep pace with high demand for food coupled with increasing aridity of the subregion, some farmers resort to informal irrigation practices. In this study, hyperspectral reflectance data of the irrigated crops under informal practices were collected to assess their efficiency of water use. Photochemical reflectance index ( ), soil-specific nitrogen index ( ), and water band index ( ) were computed. The and were significantly correlated, while there was no significant correlation between and . The map showing the probability of water stress indicated that informal irrigation practices are not an efficient water management approaches. 1. Introduction The will of individual nations to be self-sufficient has led to an increased development of irrigation facilities in recent times with potential further increases in the coming years [1]. The increase in the use of irrigation has put a serious stress on freshwater resources [2, 3]. Further development of irrigable lands and efficient management of existing ones requires knowledge of the spatial extent, of crop types, crop-evapotranspiration patterns, basin hydrology, and the impact of different types of irrigation on watersheds including inland valleys [4]. This knowledge will assist in development of a spatial decision support system to assist policy makers [5]. The Ghanaian government has recently been promoting irrigation as part of agricultural practice. However, irrigation facilities and their development are costly; hence, not all farmers are covered under state-initiated irrigation development projects. Sometimes due to poor maintenance these facilities, frequently break down rendering the farmers inactive. As a result of this lack of conventional irrigation facilities, some farmers resort to improvised ways of watering their crops. One such method is currently under way in the Atankuidi River basin in the Upper East Region of Ghana, where the inland valley is used by the communities along the river for cultivation of vegetables during the dry season. Atankuidi is a seasonal river, drying up during the dry season. During the rainy season the communities cultivate
References
[1]
P. S. Thenkabail, M. Schull, and H. Turral, “Ganges and Indus river basin land use/land cover (LULC) and irrigated area mapping using continuous streams of MODIS data,” Remote Sensing of Environment, vol. 95, no. 3, pp. 317–341, 2005.
[2]
P. S. Thenkabail, N. Gamage, and V. Smakhin, “The use of remote sensing data for drought assessment and monitoring in south west Asia,” IWMI research report number 85, IWMI, Colombo, Sri Lanka, 2004.
[3]
I. A. Shiklomanov, “Appraisal and assessment of world water resources,” Water International, vol. 25, no. 1, pp. 11–32, 2000.
[4]
D. M. Rosenberg, P. McCully, and C. M. Pringle, “Global-scale environmental effects of hydrological alterations: introduction,” BioScience, vol. 50, no. 9, pp. 746–751, 2000.
[5]
T. W. Biggs, P. S. Thenkabail, M. K. Gumma, C. A. Scott, G. R. Parthasaradhi, and H. N. Turral, “Irrigated area mapping in heterogeneous landscapes with MODIS time series, ground truth and census data, Krishna Basin, India,” International Journal of Remote Sensing, vol. 27, no. 19, pp. 4245–4266, 2006.
[6]
N. Lamaddalena and J. A. Sagardoy, “Performance analysis of on-demand pressurized irrigation systems,” FAO irrigation and drainage, paper 59, 2000.
[7]
D. Renault, T. Facon, and R. Wahaj, “Modernizing irrigation management – the MASSCOTE approach. Mapping system and services for cal operation techniques,” FAO irrigation and drainage, paper 63, 2007.
[8]
D. M. Tate and Scarf, Water use in Canadian Industry, Environment Canada, 1991.
[9]
“Chapter 1—introduction to evapotranspiration,” http://www.fao.org/docrep/x0490e/x0490e04.htm.
[10]
L. C. P. M. Stuyt, W. Dierickx, and J. M. Beltran, “Materials for subsurface land drainange systems,” FAO irrigation and drainage, paper 60, 2005.
[11]
C. W. Thornthwaite, “An approach toward a rational classification of climate,” Geographical Review, vol. 38, pp. 55–94, 1948.
[12]
P. E. Dodds, W. S. Meyer, and A. Barton, “A review of methods to estimate irrigated reference crop evapotranspiration across Australia,” Tech. Rep. number 04/05, CRC for Irrigation Futures, 2005.
[13]
B. Barry, E. Obuobie, M. Andreini, W. Andah, and M. Pluquet, “Comprehensive assessment of water management in agriculture (comparative study of river basin development and management,” 2005.
[14]
C. Leemhuis, G. Jung, R. Kasei, and J. Liebe, “The Volta Basin water allocation system: assessing the impact of small-scale reservoir development on the water resources of the Volta basin, West Africa,” Advances in Geosciences, vol. 21, pp. 57–62, 2009.
[15]
S. Opoku-Duah, D. N. M. Donoghue, and T. P. Burt, “Intercomparison of evapotranspiration over the Savannah Volta Basin in West Africa using remote sensing data,” Sensors, vol. 8, no. 4, pp. 2736–2761, 2008.
[16]
C. Gordon and J. A. Amatekpor, Eds., The Sustainable Integrated Development of the Volta Basin in Ghana. Volta Basin Research Project, Accra, Accra, Ghana, 1999.
[17]
M. Andreine, N. van de Giesen, A. van Edig, M. Fosu, and W. Andah, “Volta Basin water balance,” ZEF Discussion Paper number 21, ZEF, Bonn, Germany, 2000.
[18]
B. Barry, E. Obuobie, M. Andreini, W. Andah, and M. Pluquet, The Volta River Basin, 2005, http://www.iwmi.cgiar.org/assessment/files_new/research_projects/River_Basin_Development_and_Management/VoltaRiverBasin_Boubacar.pdf.
[19]
N. van de Giesen, J. Liebe, and G. Jung, “Adapting to climate change in the Volta Basin, West Africa,” Current Science, vol. 98, no. 8, pp. 1033–1037, 2010.
[20]
African Water Resources Database, Concepts and Applications Case Studies, vol. 109.
[21]
W. Andah, N. van de Giesen, A. Huber-Lee, and C. B. Biney, “Can we maintain food production without losing hydropower? The Volta basin (West Africa),” in Climate Change in Contrasting River Basins, J. C. J. H. Aerts and P. Droogers, Eds., pp. 181–194, CABI, Wallingford, UK, 2004.
B. Datt, “A new reflectance index for remote sensing of chlorophyll content in higher plants: tests using eucalyptus leaves,” Journal of Plant Physiology, vol. 154, no. 1, pp. 30–36, 1999.
[24]
D. A. Sims and J. A. Gamon, “Relationships between leaf pigment content and spectral reflectance across a wide range of species, leaf structures and developmental stages,” Remote Sensing of Environment, vol. 81, no. 2-3, pp. 337–354, 2002.
[25]
J. Penuelas, I. Filella, C. Biel, L. Serrano, and R. Save, “The reflectance at the 950–970？nm region as an indicator of plant water status,” International Journal of Remote Sensing, vol. 14, no. 10, pp. 1887–1905, 1993.
[26]
J. A. Gamon, J. Penuelas, and C. B. Field, “A narrow-waveband spectral index that tracks diurnal changes in photosynthetic efficiency,” Remote Sensing of Environment, vol. 41, no. 1, pp. 35–44, 1992.
[27]
J. A. Gamon, L. Serrano, and J. S. Surfus, “The photochemical reflectance index: an optical indicator of photosynthetic radiation use efficiency across species, functional types, and nutrient levels,” Oecologia, vol. 112, no. 4, pp. 492–501, 1997.
[28]
F. D. Van der Meer and S. M. de Jong, Imaging Spectrometry. Remote Sensing and Digital Image Processing, Springer, Berlin, Germany, 2006.
[29]
L. Kumar, K. Schmidt, S. Dury, and A. Skidmore, “Imaging spectrometry and vegetation science,” in Imaging Spectrometry, F. D. van der Meer and S. M. de Jong, Eds., pp. 111–155, 2006.
[30]
J. S. Boyer, “Plant productivity and environment,” Science, vol. 218, no. 4571, pp. 443–448, 1982.
[31]
R. D. Jackson, “Remote sensing of biotic and abiotic plant stress,” Annual Reviews in Phytopathology, vol. 24, pp. 265–287, 1986.
