Water-table management in lowland UK peat soils and its potential impact on CO2 emission

The rate of oxidation of peat soils is highly seasonal and varies with temperature and soil moisture content. Large variations in soil moisture content result in wet–dry cycles that can enhance peat degradation. Water‐table management plays a crucial role in controlling and damping the effect of these environmental factors. However, maintaining high ditch water levels in fields bounded by ditches does not guarantee a high field groundwater level. The effect of installing subsurface irrigation at different spacings on water table elevation was studied in a low‐lying peat grassland. The water table elevation data were compared against values predicted with a water balance model. In addition, greenhouse experiments were carried out on undisturbed soil core samples collected from the peat grassland as well as a low‐lying peatland under intensive arable faming to measure CO₂ evolution under different water regimes. The field data from the peat grassland suggest that sub‐irrigation spacing as low as 10 m is necessary during summer periods to maintain groundwater levels similar to those in the ditches. Over the same period of observation, the difference in water level between the ditches and the non‐irrigated fields is as high as 0.7 m. Modelled outputs are in good correlation with the field observations, and demonstrate that simple water balance models can provide an effective tool to study the effect of water management practices and potential changes in subsurface conditions, climate and land use on water‐table levels. The measurement of CO₂ emission from undisturbed peat soil columns shows that the rate of oxidation of soil organic matter from peat soils is highly seasonal and that drainage exacerbates the rate of peat mineralization.     

大口径埋地塑料排水管的应用前景

结合塑料排水管材的自身特点及目前这一管材在市政排水领域的应用现状，通过多年的工程实践，从国家相关的法律法规及经济技术比较等角度出发，笔者认为大口径埋地塑料排水管替代传统的钢筋混凝土排水管将成为市政工程管网建设中的新趋势。     

晒田强度和穗肥运筹对三角形强化栽培水稻光合生产力和氮素利用的影响

以杂交中稻组合II优498为材料,在三角形强化栽培(TSRI)条件下,研究3种晒田强度(0~20 cm土壤相对含水量为80%±5%、60%±5%和40%±5%,分别记为W₁、W₂和W₃)和3种穗肥运筹(晒田复水后第1、8和15天施用第1次氮素穗肥,分别记为S₁、S₂和S₃)对灌浆结实期水稻光合生产和氮素利用的影响。结果表明,晒田程度和穗肥运筹对水稻光合生产、干物质积累、氮素积累、转运和利用和产量的影响存在显著互作效应,且晒田影响最为显著,氮素穗肥运筹次之。轻度晒田(W₁)复水后第1天施用第1次氮素穗肥会降低抽穗后15 d和30 d的群体光合和有效穗数,推迟至复水后第8天或第15天施用第1次氮素穗肥可以提高抽穗后15 d和30 d的群体光合、收获指数和氮素稻谷生产效率;中度和重度晒田(W₂和W₃)复水后第1天和第8天施用第1次氮素穗肥可以提高孕穗期和齐穗期剑叶P_n和抽穗后15 d和30 d的群体光合、干物质积累、籽粒产量及构成指标、稻株氮素积累与利用。经过分析比较得出,TSRI模式下W₂S₁为晒田强度和穗肥运筹的最优组合,产量达到10.96 t ha^-1。     

Application the hydraulic fracturing technology in the highn pressure and low permeability mine

To solve the gas drainage problem of the high gas and low permeability mine, based on the features of the high pressure water, the hydraulic fracturing technology is proposed to improve the gas drainage rate. According to the first strength theory, through analyzing the stress around the borehole, the broken mechanism of the coal under high pressure is studied and the function of critical value is obtained. In addition, based on the coal features of the tenth mine of the Pingdingshan, the fracturing pressure is calculated and the hydraulic fracturing parameter is optimized. The equipment of the hydraulic fracturing technology is developed and applied successfully in the mine. And it is found that the gas drainage flux and concentration are improved with more than 5 times.     

江西东江源区森林涵养水源价值评估与保护对策

东江源区是以森林涵养水源为主导功能的国家生态功能保护区建设试点区,涵盖江西省南部的寻乌、安远、定南三县。东江是珠江三角洲和香港地区的主要饮水水源。江西东江源区流域面积3 524 km2,虽只占东江全流域面积的13%,但向珠江三角洲和香港地区的供水量约占总供水量的近40%,加强源区保护和建设,保持其优良的水质和充足的水量,直接关系到香港和珠江三角洲工农业生产和居民的生活,对香港的稳定、繁荣和珠江三角洲的可持续发展,具有特别重要的意义。目前东江源区,人口压力和强烈的经济发展需求使保护区面临严峻挑战,创新东江源区森林涵养水源保护机制,协调生态保护与经济社会发展的关系已刻不容缓。     

Groundwater governance through electricity supply management: Assessing an innovative intervention in Gujarat, western India

Gujarat, a rapidly industrializing state in western India, is notorious for groundwater over-exploitation. A perverse link between energy subsidies and groundwater overdraft has left the state with a bankrupt electricity utility and depleted aquifers, especially since the late 1980s. Moreover, this perverse relationship has meant that groundwater irrigators have essentially held Gujarat's non-farm rural economy to ransom. Efforts to regulate groundwater overdraft since the early 1970s have been unsuccessful, as have attempts to charge a rational electricity tariff to groundwater irrigators. During 2003-2006, drawing upon a proposal outlined by researchers, the government launched the Jyotigram (lighted village) scheme, which invested US$ 290 million to separate agricultural electricity feeders from non-agricultural ones, and established a tight regimen for farm power rationing in the countryside. By 2006, Gujarat covered almost all of its 18,000 villages under the Jyotigram scheme of rationalized power supply. With this, two major changes have occurred: (a) villages receive 24 h three-phase power supply for domestic uses, in schools, hospitals, village industries, all subject to metered tariff; (b) tubewell owners receive 8 h/day of power of full voltage and on a pre-announced schedule. The Jyotigram scheme has radically improved the quality of village life, spurred non-farm economic enterprises, halved the power subsidy to agriculture, and reduced groundwater overdraft. It has also produced positive and negative impacts on medium and large farmers, while notably harming marginal farmers and the landless, who depend for their access to irrigation on water markets which have become much smaller, post-Jyotigram. In addition, the water prices charged by tubewell owners have increased by 30-50%. We propose that the Jyotigram scheme, with some refinements, can be implemented successfully in other regions of South Asia facing similar challenges of groundwater governance.     

Optimized denitrification bioreactor treatment through simulated drainage containment

In the design of wood-based, enhanced-denitrification bioreactors to treat nitrate in agricultural drainage, the consideration of the highly variable flow rates and nitrate concentrations inherent to many drainage systems is important. For optimized mitigation of these nitrate loads, it may be best to contain drainage water prior to treatment in order to facilitate longer, more constant retention times rather than to allow cycles of flushing and dry periods in the denitrification bioreactor. Simulated containment prior to bioreactor treatment compared to passing drainage directly through a bioreactor was investigated with the use of six pilot-scale denitrification bioreactors constructed with plywood and filled with Pinus radiata woodchips at Massey University No. 4 Dairy Farm (Palmerston North, New Zealand). Initial bromide tracer tests were followed with a series of five simulated drainage events each at successively declining inflow nitrate concentrations. During each drainage event, three pilot bioreactors received a simulated hydrograph lasting 1.5 days (Non-Containment treatment) and three pilot bioreactors received the same total drainage volume treated over 4 days at a constant flow rate (i.e. constant retention time; Containment treatment). Results showed significantly different total mass removal efficiencies of 14.0% vs. 36.9% and significantly different removal rates of 2.1 g N m⁻³ day⁻¹ vs. 6.7 g N m⁻³ day⁻¹ for the Non-Containment and Containment treatments, respectively, which indicated that treating drainage at constant retention times provided more optimized nitrate removal. While this work was done to evaluate treatment under New Zealand drainage conditions, it also provides valuable information for optimizing agricultural drainage denitrification bioreactor performance in general.     

Evaluating the Impact of Irrigation and Drainage Policies on Agricultural Sustainability

Farmers in the Broadview Water District in central Californiahave been improving irrigation practices in response to risingirrigation water prices and reductions in water supply since1989, when incentive policies were first implemented to reducethe volume of subsurface drain water generated in theDistrict. The average salinity of water deliveries hasincreased, over time, as the District has recycled largeamounts of drainage water to achieve regional restrictions ondrainage water discharge. We review irrigation and drainageactivities in Broadview since 1986 with an emphasis on thesustainability of crop production when drainage discharge islimited. Average cotton yields in Broadview have declined inrecent years, both nominally and in comparison with averageyields reported for the large county in which Broadview islocated. Average tomato yields in Broadview have increased inrecent years, but county-wide yields have exceeded Broadviewyields with greater frequency than in the late 1980s. Theseobservations suggest that average crop yields in Broadview maybe starting to reflect the increasing salinity of soil andwater resources, which may be due in part to persistentrestrictions on drainage water discharge.     

不同毛沟布置方式下农田次降雨氮素流失特性分析

为了研究田间工程对农田氮素随径流流失的影响,该文通过设置不同排水毛沟布置方式下农田对比试验,观测研究了农田出口的降雨径流特征以及氮素流失特征,结果表明：与毛沟布置多的处理相比,毛沟布置少的处理径流对雨强变化敏感度相对较小,其径流峰值滞后,且高峰径流量持续时间长,但总氮输出负荷减少7.44%;2个处理之间铵态氮和硝态氮的流失量均差异显著;在径流初始及峰值阶段铵态氮占总氮的比例显著高于径流消减阶段,硝态氮的比例全过程变化不大;硝态氮、铵态氮、总氮的输出负荷与径流量呈线性正相关。研究表明：汇水面积小,毛沟布置多的处理减少农田涝渍效果明显,而汇水面积大,毛沟布置少的处理能有效降低总氮的输出负荷。     

Strategies for reducing subsurface drainage in irrigated agriculture through improved irrigation

The traditional approach ofinstalling subsurface drainage systems tosolve shallow ground water problems is notfeasible along the west side of the SanJoaquin Valley of California because of thelack of drain water disposal methods thatare economical, technically feasible, andenvironmentally friendly. Thus, optionssuch as drainage reduction through improvedirrigation and drain water reuse are beingexamined as methods for coping with thesubsurface drainage problem. This paperdiscusses options for reducing subsurfacedrainage through improved irrigationpractices. Options are discussed forimproving irrigation system design such asupgrading existing irrigation methods andconverting to systems with higher potentialirrigation efficiencies. Methods forimproving water management are alsopresented. Case studies on upgradingexisting systems or converting to otherirrigation methods are presented along with study results of the effect of variouspolicies on reducing subsurface drainage.