Irrigation development and its environmental consequences in arid regions of India

The present paper examines the nature and dimensions of environmental transformation induced by canal irrigation in the arid region of India. The case study pertains to the Indira Gandhi Canal comand area in Rajasthan where the density and area of vegetation cover have increased due to afforestation, and the cultivated area has expanded due to irrigation. Consequently, there has been a perceptible improvement in the structure and fertility of sandy soils, but it would require a herculean effort on the part of the canal authority and local people to reduce soil erosion and siltation in the lower parts of stage I and the entire command area of stage II. Moreover, the water table has been rising rapidly throughout the command area of stage I. About half of the command area and adjoining Ghaggar basin in Ganganagar District will be facing the danger of waterlogging by the turn of the century. The incidence of irrigation-induced alkalization is higher in the lower parts of stage I. Soil alkalinity has appeared within five years of the introduction of irrigation in the interdunal basins and is manifested as a strong salt regime or calcareous pans near surface. This calls for immediate reclamation of the affected area and prevention of its expansion by altering the strategy of irrigation development, by changing cropping patterns, and by providing soil drainage.     

Climate change, water availability and future cereal production in China

Climate scenarios from a regional climate model are used to drive crop and water simulation models underpinned by the IPCC A2 and B2 socio-economic development pathways to explore water availability for agriculture in China in the 2020s and 2040s. Various measures of water availability are examined at river basin and provincial scale in relation to agricultural and non-agricultural water demand and current and planned expansions to the area under irrigation. The objectives are to understand the influences of different drivers on future water availability to support China's food production. Hydrological simulations produce moderate to large increases in total water availability in response to increases in future precipitation. Total water demand increases nationally and in most basins, but with a decreasing share for agriculture due primarily to competition from industrial, domestic and municipal sectors. Crop simulations exhibit moderate to large increases in irrigation water demand which is found to be highly sensitive to the characteristics of daily precipitation in the climate scenarios. The impacts of climate change on water availability for agriculture are small compared to the role of socio-economic development.The study identifies significant spatial differences in impacts at the river basin and provincial level. In broad terms water availability for agriculture declines in southern China and remains stable in northern China. The combined impacts of climate change and socio-economic development produce decreases in future irrigation areas, especially the area of irrigated paddy rice. Overall, the results suggest that there will be insufficient water for agriculture in China in the coming decades, due primarily to increases in water demand for non-agricultural uses, which will have significant implications for adaptation strategies and policies for agricultural production and water management.     

Requisite Simplicities to Help Negotiate Complex Problems

Decision makers responsible for natural resource management often complain that science delivers fragmented information that is not useful at the scale of implementation. We offer a way of negotiating complex problems by putting forward a requisite simplicity. A requisite simplicity attempts to discard some detail, while retaining conceptual clarity and scientific rigor, and helps us move to a new position where we can benefit from new knowledge. We illustrate the above using three case studies: elephant densities and vegetation change in a national park, the use of rules of thumb to support decision making in agriculture, and the management of salt in irrigation. We identify potential requisite simplicities that can allow us to generate new understanding, lead to action and provide opportunities for structured learning.     

某灌区土壤中重金属镉污染调查

对沈阳市郊某污灌区土壤中重金属镉的污染状况进行了调查.结果表明,2000年土壤中镉质量比为0.23 mg/kg～5.55 mg/kg,最高值超标17.5倍;平均值为2.02 mg/kg,属严重污染,污染程度仍处在停耕前水平;污灌区土壤镉含量与土壤深度有关,深度为16 cm～30 cm污染最重,51 cm～80 cm污染最轻.     

From open access to access by all: restating challenges in designing groundwater management in Andhra Pradesh, India

In a village-based watershed in Andhra Pradesh, India, it is increasingly difficult for users to access and extract groundwater for irrigation: a 'pumping race' is taking place. A move from groundwater development towards groundwater management is required, with a new perspective on options for change. Through a study of borewell technology and groundwater use, and considering new local developments in electricity supply and participatory resource management, the article argues that groundwater is a resource with 'instructions for use'. The technological dimensions of groundwater irrigation urge its study as a socio-technical process in order to design sustainable and equitable groundwater management.     

Effect of fertilization and irrigation schedule on water and fertilizer solute transport for wheat crop in a sub-humid sub-tropical region

In order to increase the water and fertilizer use efficiency and decrease the losses of water and fertilizer solutes (N and P), it is necessary to assess the influence of level of fertilization and irrigation schedule on movement and balance of water and fertilizers in the root zone. With this goal, the reported study was undertaken to determine the effect of fertilization and irrigation schedule on water movement and fertilizer solute transport in wheat crop field in a sub-tropical sub-humid region. Field experiments were conducted on wheat crop of cultivar Sonalika (Triticum aestivum L.) during the years 2002–2003, 2003–2004 and 2004–2005. Each experiment consisted of four fertilizer treatments and three irrigation treatments during the wheat growth period. During the experiment, the irrigation treatments were: I₁ = 10% maximum allowable depletion (MAD) of available soil water (ASW); I₂ = 40% MAD of ASW; I₃ = 60% MAD of ASW. The fertilizer treatments during the experiment were: F₁ = control treatment with N:P₂O₅:K₂O as 0:0:0 kg ha⁻¹; F₂ = fertilizer application of N:P₂O₅:K₂O as 80:40:40 kg ha⁻¹; F₃ = fertilizer application of N:P₂O₅:K₂O as 120:60:60 kg ha⁻¹ and F₄ = fertilizer application of N:P₂O₅:K₂O as 160:80:80 kg ha⁻¹. The results of the investigation revealed that low volume high frequency irrigation results in higher deep percolation losses than the low frequency high volume irrigation with different levels of fertilization for wheat crop in coarse lateritic soil, whereas different levels of fertilization did not significantly affect soil water balance of the wheat crop root zone during all the irrigation schedules. Level of fertilization and irrigation schedule had significant effect on nitrogen leaching loss whereas irrigation schedules had no significant effect on nitrogen uptake under different levels of fertilization. On the other hand, the leaching loss of phosphorus was not significantly influenced by the irrigation schedule and level of fertilization of wheat crop. This indicated that PO₄–P leaching loss was very low in the soil solution as compared to nitrogen due to fixation of phosphorus in soils. From the observed data of nitrogen and phosphorus use efficiency, it was revealed that irrigation schedule with 40% maximum allowable depletion of available soil water with F₂ fertilizer treatment (N:P₂O₅:K₂O as 80:40:40 kg ha⁻¹) was the threshold limit for wheat crop with respect to nitrogen and phosphorus use, crop yield and environmental pollution.     

Irrigation and collective action: A study in method with reference to the Shiwalik Hills, Haryana

In recent years decentralized development approaches have gained prominence in the agricultural sector. A host of community based watershed management projects have been implemented that encourage community organizations to undertake management of previously government controlled irrigation systems and forests. Community organizations have been given the responsibility of managing water distribution, collection of irrigation service fees and undertaking routine maintenance of irrigation infrastructure. In this context, analysis of irrigation management has concluded that groups that are relatively homogeneous may fare better than heterogeneous groups in facilitating collective action. However, this article argues that analysis of the influence of group heterogeneity on collective action is complicated because of its multi‐dimensional nature and the presence of non‐monotonic effects in mechanisms linking heterogeneity and collective outcomes. The article discusses the importance of context specification in analysis of group heterogeneity through a discussion of elements of a joint management contract in Haryana (India), identification of key variables with a potential to explain collective action in irrigation management and construction of household endowment and water interest scores to account for the influence of group heterogeneity in facilitating collective action. In the process of applying household endowment and water interest scores, the authors highlight the role of local ecological variation and non‐farm employment in influencing collective action. Proper specification of local context enables the researchers to rely on household endowment and water interest scores to predict conflicts and potential for irrigation service provision and compliance with irrigation service rules.     

The Effects of Site Conditions and Mitigation Practices on Success of Establishing the Valley Elderberry Longhorn Beetle and Its Host Plant,Blue Elderberry

This study performed the first systematic evaluation of the success of habitat mitigation at establishing the threatened Valley elderberry longhorn beetle (Desmocerus californicus dimorphus) and its host plant, blue elderberry (Sambucus mexicana). Habitat mitigation performed through enforcement of the U.S. Endangered Species Act represents a tightly controlled form of habitat restoration, facilitating the evaluation of restoration practice. Restoration plantings of blue elderberry have been substantial in our study area, the Central Valley of California. Surveys of 30 mitigation sites and 16 nearby natural sites showed that mitigation sites were a fraction of the size of natural habitat areas (mean = 24%) and contained smaller shrubs. The beetle colonized 53% of mitigation sites and its populations were denser in sites with moderate levels of dead stems on elderberry shrubs, and moderate damage to elderberry stems and bark. This likely indicates that the beetle responds to stressed shrubs, which are likely to contain elevated levels of nitrogen. Beetle density also increased with the size and age of mitigation sites. This indicates a need to make restoration sites as large as possible and to monitor these sites for longer than current guidelines suggest, thereby allowing more time for convergence of natural and mitigation sites. Few factors examined here directly influenced the growth of elderberry shrubs, but elderberry grew more rapidly in sites closer to riparian areas, indicating that such sites should be favored for mitigation sites.     

From insight to action in reservoir management—lessons from Asia

The World Commission on Dams (WCD) has now presented its final report on the problems with large dams. Many dam projects were found to be underperforming, especially those built for irrigation purposes. WCD also reports that many projects fail to meet current standards of social equity. A reallocation of costs and benefits is needed, but entrenched interests make this a difficult task. This article identifies shortcomings in large Asian irrigation projects: why the problems emerged, and what could be done to improve the performance of existing projects. The article argues that Asian irrigation agencies take mainly an engineering perspective, focusing on the dam itself. In a large number of cases, it takes over 10 years for the infrastructure to be installed and for the water to be delivered to the fields of the command area. Agencies need to improve their competence in dealing with social and environmental issues. This article argues that social and economic infrastructure is often inadequate; there is a need for an integrated view of the role of agriculture in development. Furthermore, adaptive management practices and water user participation can often be critical elements. To be successful, participation needs to be gender sensitive, and stakeholders at all income levels need to be consulted. To bridge the gulf between rhetoric and action, there is also a need for independent evaluation of dam projects.     

地下回灌——污水回用的重要战略

介绍了污水资源化的重要技术方法——地下水回灌在战略上的重要性,并介绍了地下回灌的方法、方式、技术和国内外的现状、存在问题及发展前景。