Water balance and water use efficiency of different land uses in western Himalayan valley region

Various land uses, including sole plantations of leucaena and eucalyptus, maize–wheat, chrysopogon grass or turmeric and their tree crop mixtures were compared for period of nine years in two sequences for runoff, water use and water use efficiency on nine large erosion plots on 4% slope. Availability of water during summers and climatic evaporative (EP) demand during winters appear to be the governing factors for seasonal water use. About 70% of annual water consumption occurs during the four months (July to October) of rainy season. During this season water use was about 3–4 times to EP for trees and grass and 2.5 times for maize. The water use equals EP regardless the land use during winter season, while it reduced to about one-third to half of EP in the summer season. Annual water use is found to be closely linked with runoff reduction efficiency of the land use. Sole plantations of leucaena and eucalyptus showed negligible runoff losses and their water use approximated annual rainfall. Agroforestry land uses also reduced runoff and increased water use and water use efficiency. Seasonal crops exploited 1.5 m depth of profile more exhaustively than trees, whereas trees used soil water down to 3.0 m depth. Therefore, in tree crop mixtures more efficient soil water use was observed as compared to monocropping systems. Results of this study indicate that water conserved under sole tree plantations and due to tree intervention in agroforestry land uses through runoff reduction, is utilised to meet increased evapotranspiration demand, and hence ground water recharge in appreciable quantities is unlikely.     

Estimating episodic recharge under different crop/pasture rotations in the Mallee region. Part 2. Recharge control by agronomic practices

Much environmental degradation, including salinity in the Mallee region of southeastern Australia, is associated with the loss of native vegetation and increased recharge. As a result, various agronomic practices have been proposed to reduce groundwater recharge. This study was conducted to evaluate the impact of these practices on recharge, in particular episodic recharge. A biophysically based model (WAVES) was used to estimate recharge rates under some typical crop and pasture rotations in the region using long-term meteorological data. Results show that: (1) recharge just below the root zone was episodic and that just 10% of annual recharge events contributed over 85% of long-term totals. Management options such as incorporating lucerne and deep-rooted non-fallow rotations can reduce both, mean annual recharge, and the number of episodic events, but not eliminate recharge completely; (2) winter fallows increased soil-water storage and some of the additional water was stored in the lower portion of the root zone or below it. This can increase the risk of recharge to groundwater system; (3) changes in land management may take a considerable period of time (>10 years) to have any noticeable impacts on recharge; and (4) recharge under lucerne was ≈30% of that under medic pasture.     

An ecological optimality approach for predicting deep drainage from tree belts of alley farms in water-limited environments

The clearing of natural vegetation for agriculture in southern Australia has increased deep drainage, led to increased groundwater recharge and, hence, the salinisation of land and streams. Alley farming systems, comprising alternate belts of trees and crops, have been proposed for reducing deep drainage but their effectiveness is unknown. This paper describes an application of ecological optimality theory to estimate the equivalent no drainage (ENOD) width B (m) for a tree belt. The relative drainage RD from an alley farm, compared to conventional agriculture is, therefore, 1 − B/W, where W is the centre spacing of the belts. We present a method for estimating B_LA from the leaf area per unit length of belt LLA (m² m⁻¹), divided by the leaf area index LAI (m² m⁻²) of nearby natural vegetation. Preliminary evaluation of B_LA showed good agreement with B_WB measured from water balance and B_DD measured from deep drainage. The estimation of B_LA for calculation of RD allows rapid estimates of the relative drainage reduction expected from alley farms in water-limited environments.     

A cross disciplinary framework for linking farms with regional groundwater and salinity management targets

Irrigation delivers major benefits in food security and human development. Irrigation also leads to waterlogging and salinity which threaten the sustainability of irrigated agriculture and pose major socioeconomic and environmental risks. The issue can be addressed by limiting net recharge to groundwater such that the water and salt keep natural equilibria. Often the information on net recharge within catchments is unavailable, particularly at lower spatial scales such as the farm or paddock; this offers little guidance for on-farm land and water management decisions—basic decisions that ultimately impact regional net recharge and waterlogging and salinity dynamics. This paper develops a cross disciplinary framework based on the concept of net recharge for setting paddock scale targets and to link these to the regional targets and community's goals for sustainable irrigation management. A management model, cast in a dynamic programming format to integrate a detailed hydrological model with an economic model was applied to estimate the productivity, profitability and sustainability of irrigated agriculture in a region of the Murray Darling Basin in Australia. SWAGMAN^® Farm model was used to determine paddock scale net recharge. This interactive model enables an individual farmer to choose a profit optimizing crop mix while lowering net recharge; this in turn leads to a win-win outcome for all farmers. The net recharge metric can be used for the conversion of diffuse source groundwater recharge to a point source recharge at paddock scale, enabling the definition of private property rights to a common pool problem and assigning individual responsibilities for its management—a vexing issue and a new concept for the commons literature. Net recharge shows significant spatial and temporal variation which warrants a targeted/zonal approach to address the issue. Regional and targeted strategies and actions to address the issue are identified. Apart from its applied and action research orientation, the development of paddock scale net recharge metric is perhaps the most significant conceptual contribution of this research which can lead to shared management of groundwater aquifers.     

Standard precipitation index to track drought and assess impact of rainfall on watertables in irrigation areas

The Standard Precipitation Index (SPI) is employed to track drought and assess the impact of rainfall on shallow groundwater levels in three selected irrigation areas of the Murray-Darling Basin in Australia. The continuous SPI method can provide better means of quantifying rainfall variability and correlating it with changes of shallow watertable levels since it is based on continuous statistical functions comparing rainfall variability over the entire rainfall record. Drought analysis in the Australian irrigation areas using SPI indicates that the recent 2000–2006 drought is not the worst drought that has occurred in the recorded history, however if the current low rainfall pattern continues, it would be one of the most prolonged drought. The shallow groundwater fluctuations in the Murrumbidgee Irrigation Area show a very strong correlation with winter rainfall variation. The shallow piezometric levels in the Coleambally Irrigation Area show a weaker degree of correlation with the SPI due to local and regional groundwater dynamics and changes in rice water use. The groundwater levels in the Murray Irrigation Area show least correlation with the SPI, which may be attributed to improved irrigation management practices and complex nature of the groundwater recharge and discharge processes in this area. The overall results however show that the SPI correlates well with fluctuations in shallow ground water table in irrigation areas, and can also capture major drought patterns in Australia. The correlation of SPI with groundwater levels can be adopted for environmental reporting and used as a method of relating climatic impacts on watertables. Differences in piezometric response between years with similar winter and yearly SPI values can be attributed to improvement in irrigators’ management practices.     

土地利用方式对平原-丘陵-湿地交融区水资源的影响

近年来三江平原的平原-丘陵-湿地交融区土地利用方式变化显著,造成地下水水位下降、水资源紧缺等问题,然而揭示该区土地利用方式变化对水资源影响的报道较少,且难于精准描述地表、地下、湿地和绿水等水资源量时空变化。本文联合基于格子波尔兹曼法的分布式TOPMODEL和湿地水流运动模型构建平原-丘陵-湿地交融区水文模型,利用GIS和RS技术,结合地学信息图谱与空间自相关方法,分析了挠力河流域土地利用方式变化及其对水资源量影响。结果表明:根据耕地面积变化和动态度分布得1990—2013年间挠力河流域草地和林地面积变化不大,旱地面积轻微下降;挠力河流域中部与北部区域生产条件优越的未利用地和旱地转为水田;土地利用方式变化对水资源影响由强到弱的顺序为灌溉水田抽取地下水量、绿水储量、径流深、绿水流量、补给地下水量;水稻田不同生育期蒸发量不同,造成了挠力河流域5—6月期间绿水流量增加、绿水储量减少、径流深减少、补给地下水量增加和灌溉水田抽取地下水量增加等趋势,7—8月期间这一增加趋势逐渐减弱,8月后这一趋势结束;水田密集区域绿水流量大,绿水储量和径流深减少,而补给地下水量和灌溉水田抽取地下水量增加。     

Estimating episodic recharge under different crop/pasture rotations in the Mallee region. Part 1. Experiments and model calibration

Changes in land use in the Mallee region of southeastern Australia have led to increased groundwater recharge and salinisation. This study was conducted to determine the impact of different agronomic practices on recharge control, in particular episodic recharge. During the period 1991–1995, two field experiments were carried out at Hillston (New South Wales) and Wallpeup (Victoria) where soil hydraulic properties, soil-moisture content, and leaf area index were measured. Various crop and pasture rotations were considered involving fallow, field pea (Piscum salivum L cv Dunndale), Indian mustard (Brassica juncca cv F2 cross), wheat (Triticum aestivum cv Janz Meering), oats (Avena sateva L. cv Coolabah), lucerne (Medicago sativa L. cv. Arora) and medic pastures (Medicago truncatula cv Parriagio, Sephi and Hykon). Data obtained from these experiments were used to calibrate and test a biophysically based model WAVES. With minimum calibration, the simulated soil-moisture content and leaf area index are in good agreement with field observations. The parameter values are within a physically reasonable range. The success of the model in simulating soil-moisture dynamics and plant growth was due to the accurate representation of the soil and canopy processes. WAVES combined with field measurements provides a powerful tool for estimating the impacts of land-management options on water balance.     

基于内边缘场电容效应的树干/枝水分传感器研究

茎秆水分与茎流速率是解析植物茎秆内水分传输的2个重要参数。设计了一种基于内边缘场电容效应的树干/枝水分传感器。采用有机溶液试剂法与枝条冻融法分别对传感器做了性能测试试验,证实了传感器在相对介电常数16.8~81变化范围内具有很好的线性关系(R2=0.977 2),并从冻融-干湿等价性能看,传感器反应灵敏度满足测量要求。利用枝条脱水法得到了传感器参考标定曲线,决定系数为0.992 2。温室环境下的盆栽苹果树试验证实了该传感器既可无损观测树干细胞昼夜间的充放水过程,还可感测亏水树干内膨压崩溃与恢复过程。     

Factors driving land use change: Effects on watershed functions in a coffee agroforestry system in Lampung,Sumatra

Forest cover in Sumberjaya declined from 60% to 10% over the past three decades; current land uses are a mosaic of smallholder coffee fields on slopes, and rice paddies and vegetables in the valleys. While deforestation was continuing at the forest frontier, farmers were already ‘re-treeing’ the landscape and many monoculture coffee gardens were gradually transformed into mixed systems with shade trees. In this case study we illustrate that the factors driving deforestation were strong, interconnected and generally outside the forestry domain. The current agroforestry landscape generates a significantly higher discharge than in the past, allowing a hydropower dam to revise its power-production targets upwards. One of the main reasons given to justify the eviction of farmers in the watershed, based on claims that the past land use change would negatively affect the discharge and the dam’s power generation, proved wrong. In this area, various myths about watershed functions – already dismissed in other parts of the world – still dominate the thinking of many foresters and policymakers; this paper illustrates how and why this situation came about.     

Heat-pulse measurements of sap flow in olives for automating irrigation: tests,root flow and diagnostics of water stress

The compensation heat-pulse method for measuring sap flow is tested here in olive trees (Olea europaea L.). We describe a rigorous three-way examination of the robustness of the technique for this species, and examine the potential of the technique for an automatic control of the irrigation system. Two tests were carried out using heat-pulse gear inserted into the stem of 12-year-old ‘Manzanilla’ olive trees. One test used forced-flow through a stem section, and the other involved measured water uptake by an excised tree. The measured sap flow in these two tests was in agreement with calculations from heat-pulse velocities when using a standard ‘wound correction’ to account for the presence of the probes and the disruption to the sap flow. Thus, this technique for monitoring transpiration can, we feel, be used with confidence in olives.The third experiment was carried out in the field, where we analysed sap flow data from two 29-year-old olive trees — one tree was under regular drip irrigation and the other was from dry-farming conditions. We use measurements of sap flow in the trunk to examine the hydraulic functioning of the tree, and to explore some diagnostics of water stress. Our heat-pulse measurements in the irrigated olive tree exhibited a profile of sap flow that was weighted towards the outer xylem of the tree trunk while the water-stressed trees in the field showed a profile of sap flow weighted towards the centre of the trunk. The loss of hydraulic functioning in the outermost section of the vascular system, as a result of water stress, we consider to be due both to stomatal control and to embolisms in the xylem vessels.The fourth experiment was also carried out in the field, in which sap flow measurements were made at three locations in the trunk as well as in two roots of another 29-year-old olive tree. The soil explored by each root, on opposite sides of the trunk, was differentially wetted by separate irrigation of each side. Our data showed that the surface roots were able to absorb water immediately after wetting, despite a reasonably prolonged period of moderate drought. Root activity quickly shifted to the regions where the soil had been wetted. A root in dry soil exhibited no flow at night, whereas sap flows of about 0.02 l h⁻¹ were measured around midnight in the root drawing water from the wetter soil. Our observations suggest that the hydraulic behaviour of the trunk and surface roots might be used as a diagnostic of the onset, or severity, of water stress. Here there is not the imperative to replicate, for the prime goal is not transpiration estimation. Rather interpretation of the diurnal dynamics is used to infer the onset, or severity of water stress.The compensation heat-pulse seems a suitable technique for automatically controlling the irrigation system of olives, and probably other trees, based either on the estimation of the short-time dynamics of transpiration, or on changes in the hydraulic behaviour of the trees.     

Biophysical and economic tradeoffs of intercropping timber with food crops in the Philippine uplands

Steadily rising prices for timber on Mindanao in the Philippines have given an incentive to farmers to devote some of their land to fast-growing tree species. The costs and benefits of intercropping young timber trees with food crops was studied in a 1000 stem ha⁻¹ stand of Paraserianthes falcataria. At 2 years of age, diameter at breast height and height of intercropped trees were 33 and 21% greater, respectively, than sole trees. Management costs of intercropped trees were less than half of sole trees. Allometric equations for Mindanao falcataria were used to project future tree growth and system returns. In the base scenario (1000 trees ha⁻¹, 5-year rotation), the sum of biophysical and economic benefits of intercropping trees with a maize/vegetable rotation for two years were less than the costs of reduced intercrop yield, compared to sole cropping of each component. A linear relationship of crop decline to the increase in basal area of the stand was used to predict returns to intercropping under alternative tree densities and intercropping periods. Intercropping becomes more attractive as labor becomes scarcer relative to land, the need to minimize cash inputs becomes more important to farmers, and trees increase in value relative to annual crops.     

Species differences in transpiration on a saline discharge site

Growth, sap velocity, tree water use and transpiration rates per unit of leaf area were compared between Eucalyptus occidentalis Endl., Eucalyptus spathulata Hook., Eucalyptus leucoxylon F. Muell., and Eucalyptus cladocalyx F. Muell. on a moderately-saline discharge site near Wellington, NSW, Australia. These were four of the best performed species in a 7-year old trial of 36 species and provenances.Even though all trees were the same age and had grown under identical conditions, water use per tree was four–five times greater in E. spathulata than in the other three species. This difference was due to a large difference in tree size. E. spathulata had grown faster than the other species and had a mean tree leaf area four–five times greater than the other species.Species differences in water use per unit of leaf area were smaller, but sometimes statistically significant. During a period of cool dry weather in late winter, there were no significant differences between species in transpiration per unit of leaf area. In early summer, however, when the maximum vapour pressure deficit reached 6–7.5 kPa on some days, E. leucoxylon had a 22% lower rate of transpiration per unit of leaf area than the other three species. This difference was presumably due to a stronger stomatal response to high vapour pressure deficit in E. leucoxylon than the other species. During a period of warm humid weather in late summer, transpiration per unit of leaf area was 75% higher in E. cladocalyx compared with the other three species. The reason for this difference is not known, but it may indicate a species difference in root architecture, and hence a difference in access to ground water or soil water.     

Catchment management for dryland salinity control: Model analysis for the Liverpool plains in New South Wales

Human-induced soil salinisation is a major resource degradation issue in Australia. While the processes and remedial activities are generally understood, the pressing questions remain as to whether the problem can be managed and who should take what action. This paper presents an analysis for a catchment in Eastern Australia where dryland salinisation is emerging in the plains. A spatial and dynamic mathematical programming model is developed as a systems analysis tool. The model results establish that salinisation on the plains is caused by water imports from surrounding areas. Salinity imposes severe external costs on affected landholders who have to change their land use systems, both as a response to its emergence and to control groundwater tables. Taking a catchment perspective, it is investigated what contribution different areas within the catchment ought to make to control soil salinisation on the plains. The results indicate that some land use changes for groundwater table control would optimally be implemented in uphill recharge areas but most of the cost would be borne by plains farmers. The results also demonstrate that climatic variability tends to exacerbate salinisation and lower agricultural incomes.     

A growth-irrigation scheduling model for wastewater use in forest production

Applying wastewater and sludge to land for remediation has been recommended by the Environmental Protection Agency (EPA) as a method to recycle nutrient and organic matter and conserve water resources. The level of sewage treatment can range from simple primary treatment using a lagoon to tertiary treatment using a standard wastewater treatment plant. Small communities are selecting primary treatment and land application as the most cost-effective way of treating municipal wastewater.Wastewater was used to irrigate an Eucalyptus camaldulensis plantation in Ojinaga, Chihuahua, Mexico. The overall objective of the research was to develop a daily growth-irrigation scheduling model (GISM) for Eucalyptus tree plantations based on the trees’ water needs with the source of irrigation water being wastewater from a lagoon sewage treatment system. A second objective was to check this model against measured growth data to determine the limitations of using a simple irrigation-scheduling model to manage the irrigation system to maximize tree growth and wood production.The GISM calculated the evapotranspiration (Et) from the volume balance soil water model and a tree biomass sub-model, based on a water use efficiency (WUE) (biomass/Et) that partitions biomass determined from Et into the component parts of leaves and stems plus branches. The water balance portion of the model computes the Et for grass growing between the trees until a closed canopy system is reached. Weather data and a soil water stress function were used to calculate Et based on calculated reference Et and crop coefficients (K_cs) for both the trees and grass scaled to nonstressed Et.The GISM model accurately modeled height and diameter growth, although, it slightly overestimated the height growth of Eucalyptus for the high irrigation treatment in the second and the third years. The GISM model was successful in predicting height and diameter growth within a 95% confidence level of the measured height and diameter of the trees under all irrigation treatments.Based on the modeled and measured data analysis, the GISM model can be a useful tool to predict tree growth and schedule irrigations for Eucalyptus tree plantations, understand the trees response to environmental and water stress, and to provide better analyses for future research efforts. The climate-driving variables (temperature and rainfall) needed by the model are readily available for any location in the world from the National Climatic Data Center (NCDC).     

Estimating potential costs and gains from an aquifer storage and recovery program in Australia

Artificial recharge of aquifer storage can provide water during drought periods, reverse falling groundwater levels and reduce water losses associated with leakage and evaporation, as compared with surface water storage. We examine the technical and economic potential of artificial storage and recovery for drought mitigation in the Murrumbidgee Region of New South Wales, Australia. Potential locations for infiltration basins and injection/recovery wells are identified according to criteria such as water availability, aquifer suitability, recharge potential, and potential to provide a usable resource. The estimated annual artificial recharge potential is 180,000 ML through a combination of injection wells and infiltration basins. The cost estimates for artificial recharge vary from AU$ 62 ML⁻¹ to AU$ 174 ML⁻¹ depending on the choice of recharge method. Underground storage capacity can be developed at less than half the cost of surface storage facilities without undesirable environmental consequences or evaporation losses. The estimated benefits of artificial storage and recovery through infiltration basins are three to seven times the costs, during low allocation years.     

石漠化治理区不同植被类型浅层土壤水分对降雨的响应

【目的】揭示石漠化治理区不同植被类型浅层土壤水分入渗过程的差异性,分析降雨对土壤水分的补给特征,因地制宜地开展灌溉工作。【方法】以花椒地、金银花地、火龙果地、荒地为研究对象,监测了地区降雨量和植被0~10、10~25 cm土层土壤含水率,并计算了土壤储水量、滞后时间、补给速率、补给效率等指标。【结果】①4种植被浅层土壤含水率变化趋势与降雨一致,6、8、9月为二者的峰值期;浅层土壤含水率为火龙果地最高,而后依次为荒地、金银花地、花椒地;火龙果地土壤含水率变异系数最小,荒地最大。②植被土壤含水率对小雨量降雨事件的响应较小,仅火龙果地增长11.97%;随降雨量级增大,土壤含水率增长率为火龙果地(7.89%~17.94%),其次为金银花地(0~45.09%)、荒地(0~59.86%)、花椒地(0~126.95%);火龙果地浅层土壤含水率增长率在大雨事件中最小,其他3种样地均为小雨量时增长率小,大雨量时增长率大。③不同植被浅层土壤水分对降雨响应时间有显著差异,大雨量条件下响应快于小、中雨量,0~10 cm土层优于10~25 cm土层;平均滞后时间为荒地0.3 h、火龙果地0.5 h、花椒地0.9 h、金银花地3.0 h;补给效率为火龙果地(64.87%)>荒地(38.16%)>花椒地(31.94%)>金银花地(29.23%)。【结论】丰水期,对火龙果地适当减少人为灌溉,增加地表覆盖以减轻水土流失;对金银花地、花椒地可采取相应保墒措施提高土壤对降雨的利用效率且在雨量较小时增加灌溉,提高入渗量。     

基于立方体格网法的树冠体积计算与预估模型建立

以北京地区10种常见乔木为研究对象,通过三维激光扫描仪获取其点云数据,利用树冠表面三角网配合立方体格网法计算其树冠体积,与点云中提取所得的林木因子分析建立树冠体积和胸径、树高、平均冠幅、冠高的预估方程,并检验其精度。以银杏为研究目标进行了实验,结果表明:银杏的树冠体积与胸径、树高、平均冠幅、冠高均显著相关,通过分析选取了银杏树冠体积的三因子(胸径、平均冠幅、冠高)最优模型,并对模型进行了检验,检验结果表明,模型拟合效果较好,预估精度达到90.5%,可以使用该模型进行银杏的体积估算;同时对所选其他树种进行三因子模型拟合,模型检验结果表明,三因子模型均能够较好地对该树种的树冠体积进行估测。     

可变透光智慧膜材料板应用于果树的经济性状对比研究

将可变透光智慧膜材料应用于低纬度高原桃树种植,对比试验结果表明,应用该材料可促进试验组花芽成长率、坐果率的提升,促进果实表皮发育,进而提升果实品质,提高桃树产量,改善桃树经济性状。可变透光智慧膜材料板可以改善果园光环境,实现果实的品质与产量双丰收,可增加果树种植户的经济效益,助力产业提升。      

新疆平原区地下水资源评价误差来源分析

分析了新疆平原区地下水补给量、排泄量和可开采量评价的误差来源．提出了减少评价误差的措施：一是地下水动态监测和水运行测量统计是实现逐步逼近地下水资源量的最有效方法；二是加强基本水文及水文地质参数的试验研究；三是地下水资源评价要有动态的观念；四是建立地下水可开采量与当地地表水资源量、水利化标准间的关系：五是利用遥感技术确定土地利用现状等。     

Sensitive variables controlling salinity and water table in a bio-drainage system

Bio-drainage can be considered as an important part of sustainable irrigation water management. Bio-drainage has potential for managing shallow water conditions in arid and semiarid areas especially when traditional subsurface drains are not available. Bio-drainage theory does not go back too far. The relationship between soil characteristics, water management regimes, and climatic conditions is not yet well defined. This study attempted to use a mathematical model (SAHYSMOD) to evaluate factors affecting design and operation of a bio-drainage system and study its sensitivity to different variables. The study showed that the major constraint of bio-drainage is salt accumulation in tree plantation strips in arid and semiarid regions. Maximum soil water salinity which can be controlled by bio-drainage is around 3 dS m^?1 in rather medium run and sustainability may only be achieved where a salt removal mechanism is considered. The study also showed that the effectiveness of the system is higher where the neighboring strips are narrower. It also showed that bio-drainage is very sensitive to the amount of applied water. While the barrier depth does not have an important effect on water table draw down, it does have a great influence on lowering the salinization rate of tree plantation strips. The application of bio-drainage could be economically controversial since in humid areas water is sufficient for agricultural crops, allocating parts of the expensive land to mostly non-fruit trees may not be feasible, while in arid and semiarid regions there is usually enough cheap land to grow trees.