Status quo and present challenges of the sustainable use and management of water and land resources in Central Asian irrigation zones - The example of the Navoi region (Uzbekistan)

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Soil salinization is a major problem in many arid and agriculturally used regions and Central Asia is a prime example for this. Intensive irrigation, saline water resources, shallow groundwater tables and high evapotranspiration rates lead to the enrichment of salts in the top soils and a reduced soil productivity in the Central Asian lowlands. This is aggravated by a strong socioeconomic growth which results in an increase in the water consumption and the intensification of the farming practices (e.g. fertilizer application). This article analyses these problems for the Navoi province in Uzbekistan, a region located in the lower reaches of the Zarafshan River in the Kyzyl Kum desert. Between 2000 and 2015 detailed data on the groundwater table, groundwater salinity and the soil salinity were collected, complemented by meteorological data, soil characteristics, water use, and fertilizer statistics. Based on these datasets the ameliorate soil conditions in the Navoi irrigation zone and their temporal dynamic were assessed.The results show that both the groundwater and soil salinity have improved slightly during the last 15 years. Especially the percentages of samples with a high salinity have been reduced significantly. In 2015 only 0.7% of the irrigated soils have been categorized as highly saline while 71.3% were only slightly saline and 18.3% non-saline, while those values for the year 2000 were 6.1%, 51.5%, and 13.2%. The ameliorate soil conditions, on the other hand, have not improved accordingly, but showed a slight deterioration, even if they are overall satisfactory in 79.6% of the area. The percentage of irrigated soils with an unsatisfactory condition has increased from 3 to 13.9% between 2000 and 2014. This development is not related to any climatological, soil or groundwater parameters, so that the impacts of an increased water usage for urban and industrial purposes (and the related effects on the water quality), as well as the increased fertilizer application, seem to be a possible explanation for the observed trend.The results show the impact of the low efficiency of the irrigation and drainage system, which is outdated, not well maintained and thus often failing, on the groundwater level and the soil salinization, but also how the attempts to update the system during the recent years has led to a slight improvement of the soil and groundwater salinity.