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1.
《Agricultural Water Management》1997,34(3):247-263
Micro-sprinklers are becoming a preferred irrigation method for water application in orchards. However, there is relatively little data available to support a particular irrigation scheduling method. The objective of this study is to quantify the components of the water balance of an almond tree under micro-sprinkler irrigation. For that purpose, an experimental plot around an almond tree with an area of 2.0 m X 2.0 m without vegetation, representing about one quarter of the wetted area of the micro-sprinkler was instrumented with neutron access tubes, tensiometers and catch cans. Twenty-five access tubes with catch cans were distributed in a square grid of 0.5 m × 0.5 m, to a depth of 0.9 m. Eight pairs of tensiometers were installed at depths of 0.825 and 0.975 m within the experimental plot. During a 7-day period in August, 1995 the plot was sprinkler-irrigated on three days, and water application rates and uniformity coefficients were calculated for each irrigation event. Neutron probe readings at 15 cm depth increments and tensiometer readings were taken 4 to 6 times daily. Results showed large evaporation losses during and immediately after the irrigations. Evaporation losses of the wetted area was estimated to be between 2 and 4 mm/irrigation event. Consequently, application efficiencies were only 73–79%, the wetting of the root zone was limited to the 0–30 cm depth interval only, the soil profile was depleted of soil water, and daily crop coefficient values at days between irrigation events were between 0.6 and 0.8. The study recommends irrigation in the evening and night hours, thereby largely eliminating the evaporation losses that occur during daytime irrigation hours. 相似文献
2.
Water tension thresholds for processing tomatoes under drip irrigation in Central Brazil 总被引：3，自引：0，他引：3
Drip irrigation has the potential to save water and mitigate foliar diseases for processing tomato production in Central Brazil.
Four experiments were carried out at Embrapa Vegetables, Brasília, Brazil, to establish irrigation management strategies during
vegetative, fruit development, and maturation growth stages of drip-irrigated processing tomato. Soil water tension (SWT)
threshold values ranging from 5 to 120 kPa were evaluated. Plants growing under higher water deficit during the vegetative
stage showed root systems up to 10 cm deeper than those irrigated more frequently. Maximum fruit yield was reached when irrigations
were performed at SWT thresholds of 35, 12, and 15 kPa during vegetative, fruit development, and maturation growth stages,
respectively. Total soluble solids content was not affected by irrigation treatments during vegetative and fruit development
stages, but increased as SWT increased during fruit maturation growth stage.
相似文献
| Waldir A. MarouelliEmail: |
3.
Accurate irrigation scheduling is important to ensure maximum yield and optimal water use in irrigated cotton. This study
hypothesizes that cotton water stress in relatively humid areas can be detected from crop stress indices derived from canopy
reflectance or temperature. Field experiments were conducted in the 2003 and 2004 crop seasons with three irrigation treatments
and multiple cultivars to study cotton response to water stress. The experiment plots were monitored for soil water potential
(SWP), canopy reflectance and canopy temperature. Four crop stress indices namely normalized difference vegetative index (NDVI),
green NDVI (GNDVI), stress time (ST) index and crop water stress index (CWSI) were evaluated for their ability to indicate
water stress. These indices were analyzed with classic mixed regression models and spatial regression models for split-plot
design. Rainfall was plentiful in both seasons, providing conditions representative of irrigated agriculture in relatively
wet regions. Under such wet weather conditions, excessive irrigation decreased lint yield, indicating the necessity for accurate
irrigation scheduling. The four crop stress indices showed significant responses to irrigation treatments and strong correlation
to SWP at shallow (0.2 m) depth. Spatial regression models were able to accurately explain the effect of irrigation treatment,
while classic split-plot ANOVA models were confounded by collinearity in data across space and time. The results also verified
that extreme humidity can mask canopy temperature differences with respect to ambient temperature, adding errors to canopy
temperature-based stress indicators.
相似文献
| Sreekala G. BajwaEmail: |
4.
《Agricultural Water Management》2006,79(3):248-264
The effect of irrigation frequency on soil water distribution, potato root distribution, potato tuber yield and water use efficiency was studied in 2001 and 2002 field experiments. Treatments consisted of six different drip irrigation frequencies: N1 (once every day), N2 (once every 2 days), N3 (once every 3 days), N4 (once every 4 days), N6 (once every 6 days) and N8 (once every 8 days), with total drip irrigation water equal for the different frequencies. The results indicated that drip irrigation frequency did affect soil water distribution, depending on potato growing stage, soil depth and distance from the emitter. Under treatment N1, soil matric potential (ψm) Variations at depths of 70 and 90 cm showed a larger wetted soil range than was initially expected. Potato root growth was also affected by drip irrigation frequency to some extent: the higher the frequency, the higher was the root length density (RLD) in 0–60 cm soil layer and the lower was the root length density (RWD) in 0–10 cm soil layer. On the other hand, potato roots were not limited in wetted soil volume even when the crop was irrigated at the highest frequency. High frequency irrigation enhanced potato tuber growth and water use efficiency (WUE). Reducing irrigation frequency from N1 to N8 resulted in significant yield reductions by 33.4 and 29.1% in 2001 and 2002, respectively. For total ET, little difference was found among the different irrigation frequency treatments. 相似文献
5.
A drip-irrigation module was developed and included in an ecosystem model and tested on two independent datasets, spring and
autumn, on field-grown tomato. Simulated soil evaporation correlated well with measurements for spring (2.62 mm d−1 compared to 2.60 mm d−1). Changes in soil water content were less well portrayed by the model (spring r
2 = 0.27; autumn r
2 = 0.45). More independent data is needed for further model testing in combination with developments of the spatial representation
of below-ground variables. In a fresh-water drip-irrigated system, about 30% of the incoming water was transpired, 40% was
lost as non-productive evaporative flows, and the remainder left the system as surface runoff or drainage. Simulations showed
that saline water irrigation (6 dS m−1) caused reduced transpiration, which led to higher drainage and soil evaporation, compared with fresh water. Covering the
soil with plastic mulch resulted in an increase in yield and transpiration. Finally, two different drip-irrigation discharge
rates (0.2 and 2.5 l h−1) were compared; however the simulations indicated that the discharge rate did not have any impact on the partitioning of
the incoming water to the system. The model proved to be a useful tool for evaluating the importance of specific management
options.
相似文献
| Louise KarlbergEmail: |
6.
Establishment of shallow and restricted root systems in cotton and its impact on plant response to irrigation 总被引：1，自引：0，他引：1
Summary The effects of frequent and shallow soil wetting by surface drip irrigation on root growth, morphology, and location, and their impact on plant sensitivity to irrigation management were studied in cotton (Gossypium hirsutum L.). Daily drip irrigation, which wetted the 0 to 40-cm soil depth, encouraged root development mainly around the drippers. Water extraction took place mostly from 0 to 20 cm below the drippers, where the roots were concentrated. Shallowness of root growth was not altered by the expansion and deepening of the wetted soil zone which resulted from an increase in amount of irrigation water. The shallow and restricted root system was characterized by a high fraction of thin roots (less than 1 mm dia.) which comprised almost 90% of the root dry matter. Root proximity to the drippers and the limited amount of water in the rooted soil led to a sensitive and quick response of the plants to small amounts of irrigation. A supply of 1.0 mm H2O given at midday to 70 day-old plants resulted in a leaf water potential (L
w) increase from –1.64 to –1.32 MPa over a 20-min period. This amount of irrigation comprised 15% of the average daily quantity. A 24 h delay in irrigation to 80 dayold plants was enough to decrease L
w from –1.41 to –2.42 MPa. This decrease was caused by a soil water deficit of less than 6 mm H2O. Extending the irrigation delay to 72 h affected yield and earliness, although the deficient amount of water was supplied over the several days after the treatment. A strong response to minor, but continuous, differences in the daily irrigation amount was detected. Differences in irrigation of less than 1 mm H2O per day applied during the whole growth season substantially affected L
w, yield and earliness. It was concluded that the establishment of a shallow and restricted root system resulted in strong dependence of the plants on frequent and sufficient supply of water, and temporary minor changes in irrigation affected plant water status and productivity. 相似文献
7.
Cotton root and shoot responses to subsurface drip irrigation and partial wetting of the upper soil profile 总被引：4，自引：0，他引：4
The ability of cotton roots to grow downwards through a partially-wetted soil (Calcic Haploxeralf) profile toward a water source located beneath them was investigated. Plants were grown in 60-cm-high soil columms (diameter 10 cm), the bottom 15 cm of which was kept wet by frequent drip irrigation, while the upper 45 cm was wetted three times per week up to 20, 40, 60, 80 or 100% of pot capacity. Pot capacity was defined as the water content which gave uniform distribution within the pot and was at a soil matric potential (
m
) of –0.01 MPa. Plants were harvested 42 and 70 days after emergence (DAE). Root length density was reduced by decreased soil moisture content. At 42 DAE, density was reduced in the soil profile down to 36 cm. The density in the middle segment of the cylinder (24–36 cm) increased at the second harvest, from 0.1 to 0.35 cm · cm–3 at 40% and from 0.2 to 0.5 cm · cm–1 at 60% of pot capacity, respectively. A significant rise in root length density was found at all moisture contents above 20% in the two deepest soil segments. It was most marked at 40% where the rise was from 0.2 to 0.8 cm · cm–3, due to the development of secondary roots at the wetted bottom of the column. When only 20% of pot capacity was maintained in the top 45 cm of the profile, almost no roots reached the wetted soil volume, and root length density was very low. Hydrotropism, namely root growth through dry soil layers toward a wet soil layer was thus not apparent. Root dry weight per unit length decreased with increasing depth in the column at all moisture levels. However, the only significant decrease was, found between the top and the second soil segments and was due to thicker primary roots in the top segment. There was no clear relationship between length and dry weight of roots. Total plant dry weight and transpiration were reduced significantly only at 20% of pot capacity. Dry matter production by roots was less severely inhibited than that by shoots, under decreased moisture content in the soil profile. Leaf water potential decreased when the soil moisture content of the top 45 cm of the profile was reduced below 60% of pot capacity. It was concluded that even at soil moisture content equivalent to a
m of 0.1 MPa, the rate of root growth was sufficient to reach a wetted soil layer at the bottom of the soil column, where the plant roots then proliferated. This implies that as long as the soil above the subsurface dripper is not very dry there is no real need for early surface irrigation. 相似文献
8.
Behavior of temperature-based water stress indicators in BIOTIC-controlled irrigation 总被引：1，自引：1，他引：0
A subsurface drip irrigation study with cotton used canopy temperature to determine signals for irrigation control during 2002–2004. Timing of irrigation applications was controlled by the biologically identified optimal temperature interactive console (BIOTIC) protocol, which used stress time (ST) and a crop-specific optimum temperature to indicate water stress. ST was the cumulative daily time quantity when cotton canopy temperature exceeded 28°C. STs between 5.5 and 8.5 h in 1 h increments were irrigation signal criteria, which produced different irrigation regimes. This investigation examined the association among ST, daily average canopy temperature (T
c), canopy and air temperature difference (T
c−T
a), and the relative crop water stress index (RCWSI) including their relationship with lint yield. Number of irrigation signals decreased linearly with ST at the rate of −10.2 and −8.7 irrigations per 1 h increase of ST in 2003 and 2004. There were significant curvilinear relationships between ST and the average daily stress on days with irrigation signals and for days without irrigation signals across years. The percentage of positive daily (T
c−T
a) values increased with ST level. ST and T
c were positively related in all irrigation signal treatments with 5.5 and 6.5 h being significant in 2003 and 2004. Yield declined at the rate of 343 kg lint/ha for each 1 h increase of ST for days with irrigation signals. ST, mathematically the most simple of the canopy temperature-based parameters, provided the most consistent estimate of crop water stress and correlation with lint yield. The power of ST to characterize water stress effects on crop productivity evolves from being an integrated value of time while canopy temperature exceeds a physiologically based threshold value.
相似文献
| D. F. WanjuraEmail: Phone: +1-806-7235241Fax: +1-806-7235272 |
9.
Impact of research on water use for irrigation in Israel 总被引：1，自引：1，他引：0
Marcel Fuchs 《Irrigation Science》2007,25(4):443-445
The decrease of annual irrigation application rate observed since 1950 was reversed in 1988 as a result of a sudden increase
of the amount of treated effluents used for irrigation. Intensification of research on irrigation with effluents and marginal
water starting in 1994 resulted four years later in the renewal of the decrease of irrigation application rate.
Contribution No. 614/06 from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
相似文献
| Marcel FuchsEmail: |
10.
Irrigation scheduling requires an operational means to quantify plant water stress. Remote sensing may offer quick measurements with regional coverage that cannot be achieved by current ground-based sampling techniques. This study explored the relation between variability in fine-resolution measurements of canopy temperature and crop water stress in cotton fields in Central Arizona, USA. By using both measurements and simulation models, this analysis compared the standard deviation of the canopy temperature
to the more complex and data intensive crop water stress index (CWSI). For low water stress, field
was used to quantify water deficit with some confidence. For moderately stressed crops, the
was very sensitive to variations in plant water stress and had a linear relation with field-scale CWSI. For highly stressed crops, the estimation of water stress from
is not recommended. For all applications of
one must account for variations in irrigation uniformity, field root zone water holding capacity, meteorological conditions and spatial resolution of T
c data. These sensitivities limit the operational application of
for irrigation scheduling. On the other hand,
was most sensitive to water stress in the range in which most irrigation decisions are made, thus, with some consideration of daily meteorological conditions,
could provide a relative measure of temporal variations in root zone water availability. For large irrigation districts, this may be an economical option for minimizing water use and maximizing crop yield.
相似文献
| M. P. González-DugoEmail: Phone: +34-957-016030Fax: +34-957-016043 |
11.
《Agricultural Water Management》2001,52(1):33-52
In order to study the use of water irrigation in a rational way, several combinations of discharge rate, irrigation duration and inter-emitter distances were tested. For instance, three dripper spacings of 30, 50 and 70 cm which delivered water volumes of 4, 8 and 16 l per dripper, respectively, and three discharge rates of 2, 4 and 8 l/h for each spacing, were applied.An overlapping of the wetted bulbs was observed at the end of the different irrigation experiments. The inter-dripper root-zone had an average water content of 45% and a coefficient of uniformity of 90%.The discharge rate of 2 l/h applied to a 70 cm dripper spacing was characterised by water losses of 15% due to the significant irrigation duration (8 h).From this study, we reach the following conclusions, specific to the soil type and practical culture.
- 1.The maximum irrigation duration does not exceed 4 h.
- 2.Two hours durations can be used for the different spacings, each of which was characterised by its own discharge rate.
12.
Opportunities for water saving with higher yield from the system of rice intensification 总被引：1，自引：0，他引：1
The system of rice intensification (SRI) developed in Madagascar, is showing that by changing the management of rice plants,
soil, water and nutrients it can increase the yields of irrigated rice by 25–50% or more while reducing water requirements
by an equivalent percent. This gives farmers incentive to reduce their irrigation water use when growing rice, especially
since SRI methods can also reduce farmers’ costs of production which increases their net income ha−1 by even more than yield. Even though these results sound fantastic, the validity of SRI concepts and practices has been demonstrated
in more than 20 countries to date. This article considers, first, the methods that make these improvements possible and how
these are achieved. It then briefly surveys SRI experience in five Asian countries, incentives in addition to yield, water-saving
and profitability for adopting SRI, and possible limitations or disadvantages with the methodology. Next, it comments on the
debate over SRI in the agronomic literature and then adds to the empirical record by reporting in some detail on SRI evaluations
in two of India’s main rice-growing states, Andhra Pradesh and Tamil Nadu, where water availability is becoming more problematic
and where SRI use is spreading. Finally, the article briefly discusses some implications of saving irrigation water by changing
resource management rather than by using on more or different inputs.
相似文献
| Norman UphoffEmail: |
13.
Laboratory evaluation of dual-frequency multisensor capacitance probes to monitor soil water and salinity 总被引：1，自引：0，他引：1
Real-time information on salinity levels and transport of fertilizers are generally missing from soil profile knowledge bases.
A dual-frequency multisensor capacitance probe (MCP) is now commercially available, for sandy soils, to simultaneously monitor
volumetric soil water content (VWC) measured as a percentage and salinity as a unitless volumetric ion content (VIC). The
objectives of this research were to assess the relationship of salinity and water content with these dual-frequency MCPs under
laboratory conditions, and assess its potential for field use in sandy soils of the mid-Atlantic region of the US. Water and
salinity studies were conducted in two sand-filled PVC columns, 1.2 m long by 0.25 m ID. Each column was instrumented with
ten dual-frequency capacitance sensors and two thermocouple temperature sensors. Four salinity levels were studied in the
two columns using 0.5, 1, 2, and 4 dSm−1 NH4NO3 solutions. Water, salinity, and temperature readings were continuously recorded at 1-min intervals. The VIC values were found
to be primarily qualitative, but combined with real-time VWC measures the probe could still be an important fertigation management
tool to provide near-continuous real-time information on fertilizer penetration, spread and subsequent changes during crop
growth.
相似文献
| J. L. StarrEmail: |
14.
The impact of small-scale irrigation on household food security: The case of Filtino and Godino irrigation schemes in Ethiopia 总被引：1，自引：0，他引：1
Abonesh Tesfaye Ayalneh Bogale Regassa E. Namara Dereje Bacha 《Irrigation and Drainage Systems》2008,22(2):145-158
Ethiopia’s irrigation potential is estimated at 3.7 million hectare, of which only about 190,000 ha (4.3% of the potential)
is actually irrigated. There is little information on the extent to which the so far developed irrigation schemes have been
effective in meeting their stated objectives of attaining food self-sufficiency and eradicating poverty. Therefore, the aim
of this paper is to identify the impact of small-scale irrigation on household food security based on data obtained from 200
farmers in Ada Liben district of Ethiopia in 2006. The resulting data was analyzed using Heckman’s Two-step Estimation procedure.
Studies elsewhere revealed that access to reliable irrigation water can enable farmers to adopt new technologies and intensify
cultivation, leading to increased productivity, overall higher production, and greater returns from farming. Our study findings
confirm some of these claims. In the study area about 70% of the irrigation users are food secure while only 20% of the non-users
are found to be food secure. Access to small scale irrigation enabled the sample households to grow crops more than once a
year; to insure increased and stable production, income and consumption; and improve their food security status. The study
concludes that small-scale irrigation significantly contributed to household food security.
相似文献
| Dereje BachaEmail: |
15.
The 2-year field experiments were carried out to research the effect of different irrigation methods, namely border irrigation,
sprinkler irrigation, and surface drip irrigation, on root development and profile water uptake in winter wheat. Results showed
that the main root distribution zone moved upward under sprinkler and surface drip irrigation when compared to the traditional
border irrigation. Profile root distribution pattern changed with irrigation methods. Soil profile water uptake was correlated
to the root system and soil water dynamics. Due to the appropriate soil water and higher root density in the surface soil
layer under sprinkler and surface drip irrigation, the main water uptake zone was concentrated in the upper layer. Because
of the water deficit in the surface layer under border irrigation, water uptake in 50–100 cm depth was stimulated, which caused
the main uptake zone downward. The amount and pattern of root water uptake varied with irrigation methods. This may provide
valuable information on the aspect of agricultural management. 相似文献
16.
《Agricultural Water Management》1997,33(1):63-78
The oft-touted reason for the efficiency of drip irrigation is that roots can preferentially take up water from localised zones of water availability. Here we provide definitive evidence of this phenomenon. The heat-pulse technique was used to monitor rates of sap flow in the stem and in two large surface roots of a 14 year old apple tree (Malus domestica Borkh. cv. Braeburn). The aim was to determine the ability of an apple tree to modify its pattern of root water uptake in response to local changes in soil water content. We monitored the water status of the soil close to the instrumented roots by using time domain reflectometry (TDR) to measure the soil's volumetric water content, θ, and by using ceramic-tipped tensiometers to measure the soil's matric pressure head, h. A variation in soil water content surrounding the two roots was achieved by supplying a single localised irrigation to just one root, while the other root remained unwatered. Sap flow in the wetted root increased straight away by 50% following this drip irrigation which wetted the soil over a zone of approximately 0.6 m in diameter and 0.25 m in depth. Sap flow in the wetted root remained elevated for a period of about 10 days, that is until most of the irrigation water had been consumed. A comparative study of localised and uniform irrigation was then made. Following irrigation over the full root zone no further change in sap flow in the previously wetted root was observed when referenced to the corresponding sap flow measured in the stem of the apple tree. However sap flow in the previously dry root responded to subsequent irrigations by increasing its flow rate by almost 50%. These results show that apple roots have the capacity to transfer water from local wet areas at much higher rates than normally occurs when the entire root zone is supplied with water. They are also able to shift rapidly their pattern of uptake and begin to extract water preferentially from those regions where it is more freely available. Such an ability supports the use of drip irrigation for the efficient use of scarce water resources. We conclude that the soil-to-root pathway represents a major resistance to water uptake by apple, even at the relatively high soil water pressure heads developed during parts of this experiment, during which the tree was not even under any stress. 相似文献
17.
Daily evapotranspiration estimates from extrapolating instantaneous airborne remote sensing ET values 总被引：1，自引：1，他引：0
José L. Chávez Christopher M. U. Neale John H. Prueger William P. Kustas 《Irrigation Science》2008,27(1):67-81
In this study, six extrapolation methods have been compared for their ability to estimate daily crop evapotranspiration (ETd) from instantaneous latent heat flux estimates derived from digital airborne multispectral remote sensing imagery. Data used
in this study were collected during an experiment on corn and soybean fields, covering an area of approximately 12 × 22 km,
near Ames, Iowa. ETd estimation errors for all six methods and both crops varied from −5.7 ± 4.8% (MBE ± RMSE) to 26.0 ± 15.8%. Extrapolated ETd values based on the evaporative fraction (EF) method better compared to eddy covariance measured ET values. This method reported
an average corn ETd estimate error of −0.3 mm day−1, with a corresponding error standard deviation of 0.2 mm day−1, i.e., about 5.7 ± 4.8% average under prediction when compared to average ETd values derived from eddy covariance energy balance systems. A solar radiation-based ET extrapolation method performed relatively
well with ETd estimation error of 2.2 ± 10.1% for both crops. An alfalfa reference ET-based extrapolation fraction method (ETrF) yielded an overall ETd overestimation of about 4.0 ± 10.0% for both crops. It is recommended that the average daily soil heat flux not be neglected
in the calculation of ETd when utilizing method EF. These results validate the use of the airborne multispectral RS-based ET methodology for the estimation
of instantaneous ET and its extrapolation to ETd. In addition, all methods need to be further tested under a variety of vegetation surface homogeneity, crop growth stage,
environmental and climatological conditions.
相似文献
| José L. Chávez (Corresponding author)Email: |
| Christopher M. U. NealeEmail: |
| John H. PruegerEmail: |
| William P. KustasEmail: |
18.
Comparing deep drainage estimated with transient and steady state assumptions in irrigated vertisols
Chloride mass balance (steady state or transient state) models are used extensively in Vertisols of Queensland and New South Wales (NSW) in Australia to estimate deep drainage. The aim of this study was to compare deep drainage estimated assuming steady state and transient state conditions with chloride mass balance models in irrigated cotton (Gossypium hirsutum L.)-based farming systems in the lower Namoi Valley of North Western NSW. Drainage was estimated at seven sites, and treatments included rotation crops such as wheat (21–62 mm/year) (Triticum aestivum), sorghum (12–47 mm/year) (Sorghum bicolor) and dolichos (12–21 mm/year) (Lablab purpureus), minimum tillage (62–83 mm/year), where cotton was sown into standing wheat stubble, and conventional tillage where stubble was incorporated (35–78 mm/year). Soil water content was measured with a neutron moisture meter in the 0.2–1.2 m depth. Soil was sampled before sowing and after harvest to a depth of 1.2 m along diagonal transects. The soil chloride concentration was determined by titration with AgNO3. Irrigation water was also analysed for chloride. The deep drainage estimates were compared using regression analysis and students paired t-test. In addition, a paired t-test of the soil chloride concentration before sowing and after harvest was used to determine if the soil chloride flux was either in a steady state or transient state. In 9 out of the 13 data sets (69%), drainage estimated with the models agreed with changes between pre- and post-season soil chloride concentrations. Under frequently irrigated summer crops such as cotton and sorghum and in better structured soils chloride flux reached steady state conditions whereas under partially-irrigated crops or where soil structure was poorer, the chloride flux deviated markedly from steady-state conditions. The latter observation may be due to preferential flow via deep cracks in infrequently irrigated soil. Deep cracking would be due to the more intense shrinking and swelling in partially irrigated soil in comparison with frequently-irrigated crops. Comparison of estimated deep drainage with pre- and post-season soil chloride concentrations showed that the steady state mass balance model best estimated deep drainage under cotton crops which were irrigated more frequently or wheat crops which had better soil structure.
相似文献
| T. B. WeaverEmail: Phone: +61-2-67991570Fax: +61-2-67991503 |
19.
Recharge to the aquifer through seepage from irrigation canals is often quoted as one of the main causes for waterlogging
in Pakistan. In the design of drainage systems to control this waterlogging, rules-of-thumb are often used to quantify the
seepage from canals. This paper presents the option to use a groundwater model for a more detailed assessment. Groundwater
models may assist in evaluating the effect of recharge reducing measures such as interceptor drains along irrigation canals
and lining. These measures are commonly aimed at reducing the drainage requirement of adjacent agricultural lands.
In this paper an example is given of the application of a numerical groundwater model, aimed at assessing the effect of interceptor
drainage and canal lining in the Fordwah Eastern Sadiqia project, being a typical and well-monitored location in Pakistan.
The paper also presents references to other conditions. The model was used to obtain a better insight in the key hydraulic
parameters, such as the infiltration resistance of the bed and slopes of irrigation canals, the drain entry resistance of interceptor drains and the hydraulic conductivity of soil layers. The model was applied to assess the effectiveness and efficiency of interceptor drains under various conditions.
The results of the study show that the net percentage of intercepted seepage is too low to have a significant effect on the drainage requirement of the adjacent agricultural lands. Besides, the operation
of the system, with pumping required, is often an added headache for the institution responsible for operation of the system.
The marginal effect of interceptor drains and lining on the drainage requirement of adjacent agricultural land does not always
justify the large investments involved. It can be concluded that:
Relevant hydrological concepts and modelling parameters with respect to leakage from irrigation canals and interception by
interceptor drains are presented in a separate paper. 相似文献
| • | Use of rules-of-thumb to estimate components of the water balance of irrigation systems in designing drainage can be very misleading; |
| • | Interceptor drainage may cause induced seepage from irrigation canals, which is often an order of magnitude more than the net intercepted seepage; |
| • | Interceptor drains and canal lining do not significantly reduce the drainage requirements, or in other words, cannot prevent the need for the installation of a drainage system; |
| • | A numerical model can aid to evaluate proposed measures and strategies to alleviate water losses and drainage problems. |