Surface Water Irrigation Research Articles

Origin and characteristics of brackish groundwater in Abu Madi coastal area, Northern Nile Delta, Egypt

Hydrogeochemical and geoelectrical resistivity investigations were carried out to assess the origin and characteristics of a brackish groundwater in Abu Madi coastal area. Twenty six surface water, shallow and deep groundwater samples were collected and analyzed for various ionic concentrations as well as oxygen and hydrogen stable isotopic contents. In addition, a total of 20 vertical electrical sounding sites were conducted to investigate layers’ thicknesses, resistivities, and to detect the water-bearing layers. Then, 2-D Electrical Resistivity Tomography (ERT) along two profiles in the study area was conducted to get information about the surface water effect on recharge. The stable isotopic composition and the chloride concentrations strongly suggest that the deep groundwater in Abu Madi area is dominated by inland freshwater with a minor seawater component. This groundwater was recharged during the first and the third Holocene humid climatic cycles where the sea surface was about 125 and 25 m below the current sea level, respectively. The brackish nature and higher piezometric surface of the groundwater, as well as the occurrence of vertical low-salinity seawater zone in front of the study area, support the possibility of submarine groundwater discharge. The geoelectrical resistivity surveying, on the other hand, revealed a number of geoelectrical groundwater-bearing layers. The main water-bearing layer in the study area is represented by the sixth geoelectrical layer, which has relatively high resistivity and a considerable thickness being consistent with the hydrogeochemical observations. ERT results point to the presence of shallow water-bearing layers recharged from the surface water drains with low resistivity and surface rain water of moderate resistivity. Results from the hydrogeochemical analyses and the different hydrogeological data are consistent with the high resistivity values of this geoelectrical layer. However, the overall high specific conductance and high sodium hazards indicate that the groundwater in the study area should be carefully treated before irrigation and domestic uses through mixing it with surface irrigation water.

Soil nitrous oxide emissions in forage systems fertilized with liquid dairy manure and inorganic fertilizers

Intensive dairy production generates large amounts of manure, which is typically reused as fertilizer for the production of forage. In the Central Valley of California, application of manure often results in high inputs of N and labile organic C, a combination that can lead to large nitrous oxide (N2O) emissions. The present study included dairy forage production fields at three dairies with a range of soil textures. Liquid manure from lagoons was applied in surface irrigation water in addition to inorganic N fertilizers. Nitrogen inputs, N2O emissions, crop N removal, soil inorganic N, moisture, and temperature were assessed over two summer corn and one winter forage seasons at each dairy. Between 0.76 and 1.30% of the applied total N was emitted as N2O annually. A significant portion of the N2O emissions was explained by high soil moisture, soil inorganic N, and soil temperature, as shown by multiple regression analysis. Variability in total N2O emissions and emission patterns was likely due to differences in N management and soil texture. Large single applications of N when crop N uptake potential was low were responsible for the largest N2O emissions, whereas distributing N additions, applied with the irrigation water, over the cropping season resulted in lower emissions. The field study was complemented with laboratory incubations of soil amended with liquid manure and 15N-labeled urea-ammonium-nitrate (UAN) to determine the proportion of liquid manure and fertilizer N emitted as N2O. The incubation results showed that liquid manure stimulated the release of N2O originating from fertilizer N. Therefore, liquid manure should not be added to irrigation water following side dress fertilizer N applications. To reduce the risks of N2O emissions and other N losses to the environment, manure and fertilizer N inputs, as well as soil N mineralization, must be accounted for and N supplied in increments according to crop demand.

Groundwater intensive use and mining in south-eastern peninsular Spain: Hydrogeological, economic and social aspects

Intensive groundwater development is a common circumstance in semiarid and arid areas. Often abstraction exceeds recharge, thus continuously depleting reserves. There is groundwater mining when the recovery of aquifer reserves needs more than 50years. The MASE project has been carried out to compile what is known about Spain and specifically about the south-eastern Iberian Peninsula and the Canary Islands. The objective was the synthetic analysis of available data on the hydrological, economic, managerial, social, and ethical aspects of groundwater mining. Since the mid-20th century, intensive use of groundwater in south-eastern Spain allowed extending and securing the areas with traditional surface water irrigation of cash crops and their extension to former dry lands, taking advantage of good soils and climate. This fostered a huge economic and social development. Intensive agriculture is a main activity, although tourism plays currently an increasing economic role in the coasts. Many aquifers are relatively high yielding small carbonate units where the total groundwater level drawdown may currently exceed 300m. Groundwater storage depletion is estimated about 15km3. This volume is close to the total contribution of the Tagus-Segura water transfer, but without large investments paid for with public funds. Seawater desalination complements urban supply and part of cash crop cultivation. Reclaimed urban waste water is used for irrigation. Groundwater mining produces benefits but associated to sometimes serious economic, administrative, legal and environmental problems. The use of an exhaustible vital resource raises ethical concerns. It cannot continue under the current legal conditions. A progressive change of water use paradigm is the way out, but this is not in the mind of most water managers and politicians. The positive and negative results observed in south-eastern Spain may help to analyse other areas under similar hydrogeological conditions in a less advanced stage of water use evolution.

Suitability Assessment of Surface Water for Irrigation in Galma Floodplain, Zaria, Kaduna State North Western, Nigeria

Suitability Assessment of Surface Water for Irrigation in Galma Floodplain, Zaria, Kaduna State North Western, Nigeria

Biophysical and economic water productivity of dual-purpose cattle farming

This study analyzes key factors influencing water productivity in cattle rearing, particularly in contexts characterized by water scarcity. This was done through year-round monitoring of on-farm practices within five smallholder farms located in the Saïss area (northern Morocco). The on-farm monitoring protocol consisted of characterizing: (i) volumes of water used for fodder production and distinguished by source (rainfall, surface irrigation and groundwater), (ii) virtual water contained in off-farm feed resources, (iii) total forage biomass production, (iv) dietary rations fed to lactating cows and their calves and (v) milk output and live weight gain. Findings reveal a mean water footprint of 1.62±0.81 and 8.44±1.09 m3/kg of milk and of live weight gain, respectively. Groundwater represented only 13.1% and 2.2% of the total water used to get milk and live weight gain, respectively, while rainfall represented 53.0% and 48.1% of the total water for milk and live weight gain, respectively. The remaining water volumes used came from surface irrigation water (7.4% for milk and 4.0% for live weight gain) and from virtual water (26.5% for milk and 44.7% for live weight gain). The results also revealed a relatively small gross margin per m3 of water used by the herd, not exceeding an average value of US $ 0.05, when considering both milk and live weight. Given the large variability in farm performances, which affect water productivity in cattle rearing throughout the production process, we highlight the potential for introducing a series of interventions that are aimed at saving water, while concurrently improving efficiency in milk production and live weight gain. These interventions should target the chain of production functions that are implemented throughout the process of water productivity in cattle rearing. Moreover, these interventions are of particular importance given our findings that livestock production depends largely upon rainfall, rather than groundwater, in an area afflicted with sustained droughts, overexploitation of groundwater resources and growing water scarcity.

Impacts of Climate and Management Variables on the Contamination of Preharvest Leafy Greens with Escherichia coli

The observed seasonality of foodborne disease suggests that climatic conditions play a role and that changes in the climate may affect the presence of pathogens. However, it is hard to determine whether this effect is direct or whether it works indirectly through other factors, such as farm management. This study aimed to identify the climate and management variables that are associated with the contamination (presence and concentration) of leafy green vegetables with E. coli. This study used data about E. coli contamination from 562 leafy green vegetables (lettuce and spinach) samples taken between 2011 and 2013 from 23 open-field farms in Belgium, Brazil, Egypt, Norway, and Spain. Mixed-effect logistic and linear regression models were used to study the statistical relationship between the dependent and independent variables. Climate variables and agricultural management practices together had a systematic influence on E. coli presence and concentration. The variables important for E. coli presence included the minimum temperature of the sampling day (odds ratio = 1.47), region, and application of inorganic fertilizer. The variables important for concentration (R(2) = 0.75) were the maximum temperature during the 3 days before sampling and the region. Temperature had a stronger influence (had a significant parameter estimate and the highest R(2)) than did management practices on E. coli presence and concentration. Region was a variable that masked many management variables, including rainwater, surface water, manure, inorganic fertilizer, and spray irrigation. Climate variables had a positive relationship with E. coli presence and concentration. Temperature, irrigation water type, fertilizer type, and irrigation method should be systematically considered in future studies of fresh produce safety.

Effect of irrigation sources and nutrient management on arsenic accumulation in vegetable pea (<italic>Pisum Sativum</italic> L.) in deltaic West Bengal, India

An experiment was conducted at Nonaghata-Uttarpara village under Haringhata block in Nadia district during successive <italic>rab</italic><italic>i</italic> seasons of 2007-08 and 2008-09 to study the arsenic contamination in vegetable pea cv. Karishma and to explore possibilities of offloading the accumulation through nutrient management using harvested surface water for irrigation. The experiment has been laid out with two irrigation sources in main plot I<sub>1</sub>: irrigation from Shallow Tube Well (STW) and I<sub>2</sub>: irrigation from Pond Water (PW) and four nutrient management options in sub-plot [N<sub>1</sub>: 100% RDF (60-80-90 kg ha<sup>−1</sup> N, P<sub>2</sub>O<sub>5</sub> and K<sub>2</sub>O), N<sub>2</sub>: 100% RDF with double the recommended dose of phosphate, N<sub>3</sub>: 75% RDF + FYM @ 10 t ha<sup>−1</sup>, N<sub>4</sub>: 75% RDF + FYM @ 10 t ha<sup>−1</sup> with double dose of phosphate] in a split plot design, replicated three times. Results revealed that pod yield did not significantly vary with different irrigation sources, but arsenic accumulation and uptake was the lowest with irrigation from harvested rain water i.e. pond water. 75% RDF + 10 t ha<sup>−1</sup> of FYM with increased phosphate recorded the maximum yield with the least arsenic accumulation (N<sub>4</sub>).

Estimation of human‐induced changes in terrestrial water storage through integration of GRACE satellite detection and hydrological modeling: A case study of the Yangtze River basin

AbstractQuantifying the human effects on water resources plays an important role in river basin management. In this study, we proposed a framework, which integrates the Gravity Recovery and Climate Experiment (GRACE) satellite estimation with macroscale hydrological model simulation, for detection and attribution of spatial terrestrial water storage (TWS) changes. In particular, it provides valuable insights for regions where ground‐based measurements are inaccessible. Moreover, this framework takes into account the feedback between land and atmosphere and innovatively put forward several suggestions (e.g., study period selection, hydrological model selection based on soil moisture‐climate interactions) to minimize the uncertainties brought by the interaction of human water use with terrestrial water fluxes. We demonstrate the use of the proposed framework in the Yangtze River basin of China. Our results show that, during the period 2003–2010, the TWS was continually increasing in the middle and south eastern reaches of the basin, at a mean rate of about 3 cm yr−1. This increment in TWS was attributed to anthropogenic modification of the hydrological cycle, rather than natural climate variability. The dominant contributor to the TWS excess was found to be intensive surface water irrigation, which recharged the water table in the middle and south eastern parts of the basin. Water impoundment in the Three Gorges Reservoir (TGR) is found to account for nearly 20% of the human‐induced TWS increment in the region where the TGR is located. The proposed framework gives water managers/researchers a useful tool to investigate the spatial human effects on TWS changes.

Energetic, Hydraulic and Economic Efficiency of Axial Flow and Centrifugal Pumps for Surface Water Irrigation in Bangladesh

AbstractWith conventional centrifugal (CEN) pumps, less than 50% of southern Bangladesh's farmers invest in irrigation, partly due to high diesel energy costs. New policies are prioritizing sustainable crop intensification in Bangladesh's delta. This objective is unlikely to be achieved without fundamental changes in the energetics and economics of irrigation. Where surface water is available, axial flow pumps (AFPs) may comprise part of the solution to this problem. Comparing the hydraulic, energetic and economic performance of prototype AFPs and CEN pumps, the latter produced less yet consistent rates of discharge than AFPs at all heads. AFP discharge was conversely larger than CEN pumps, but inversely related to increasing head. Discharge per unit of fuel was highest for AFPs (+51 and +21% at 1‐ and 2‐m lifts), but declined with rising head until convergence with CEN pumps at 2.8 m. High AFP discharge reduced irrigation time requirements. On average, AFPs can save between US$70 and 38 ha–1 season–1 for boro rice at 1‐ and 3‐m heads, respectively, and between US$15 and 8, and 26 and 14 ha–1 season–1 for wheat and maize. Fuel efficiency reductions above 2.8 m highlight the importance of improved prototyping and technology targeting to ensure AFP deployment in environments where the greatest efficiency gains are achievable. Copyright © 2015 John Wiley & Sons, Ltd.

The impact of irrigation development on regional groundwater resources in Bangladesh

There is increasing concern over falling groundwater levels in some areas of Bangladesh, and there is undoubted overuse of groundwater in the Barind Tract in northwest Bangladesh and around Dhaka. However, the volumes of water availability and use, and hence the sustainability of use, are not well known. We developed monthly water balances for the main regions of Bangladesh to investigate historic trends in water use and availability and possible future trends under changed management to lessen groundwater use by using more surface water for irrigation. Our results show that for many areas the fall in pre-monsoon groundwater levels (at the regional average level) over the last few decades may be largely explained by the continual withdrawal of ever greater volumes of water with the three-fold increase in the area of irrigation. Thus, for many areas, if there were no further increase in the area irrigated by groundwater, the rate of decline in groundwater levels would likely reduce and levels could even attain a new equilibrium at a lower level, implying that current pumping rates could be maintained (subject to the lower groundwater levels being acceptable on environmental, economic and social grounds). Post-monsoon groundwater levels are largely influenced by yearly rainfall variability. Thus, groundwater use in some areas may not be as unsustainable as feared, and policies to reduce groundwater use in such areas may not be as necessary or urgent as thought. However, our analysis is approximate and detailed local studies are required to assess the sustainability of use.

Rice productivity in Bangladesh: What are the benefits of irrigation?

Green Revolution technologies transformed Bangladesh’s agricultural system through the introduction of high-yielding rice and wheat varieties, chemical fertilizers and pesticides, and the expansion of tubewell-irrigated area, enabling crop production during the dry season. However, serious challenges continue to plague the agriculture sector, including scarcity of land due to high population density, unbalanced use of fertilizers and pesticides, and great variation in water supply across seasons – from drought to stagnant flood conditions. Further expansion of irrigated area – including through the continued development and improvement of surface water systems – is being eyed by Bangladesh’s Ministry of Agriculture to address many of the remaining challenges facing the country. However, such expansion is not without risks or consequences, and a careful analysis of who benefits from irrigation, and how, must guide development priorities.We examine plot-level data for rice production during Bangladesh’s three rice seasons – aus, boro, and aman – across a nationally-representative household survey in Bangladesh. While rainfall is the most important determinant of rice yield during aus and chemical inputs are most important during aman, access to irrigation has the greatest influence on boro rice yield during the dry season, particularly for the coastal south. The government of Bangladesh is planning massive investments in the southern region for the improved provision of surface water irrigation. The expected decline in groundwater, coupled with our econometric findings, suggests that expanding boro production in the south may not be a good strategy to promote, for the region. Whether brackish shrimp aquaculture can provide an equitable and sustainable livelihood alternative should continue to be a focus of research.

Analysis of shallow-groundwater dynamic responses to water supply change in the Haihe River plain

Abstract. When the middle route of the South-to-North Water Diversion Project is completed, the water supply pattern of the Haihe River plain in North China will change significantly due to the replenishment of water sources and groundwater-exploitation control. The water-cycle-simulation model – MODCYCLE, has been used in simulating the groundwater dynamic balance for 2001–2010. Then different schemes of water supply in 2020 and 2030 were set up to quantitatively simulate the shallow-groundwater dynamic responses in the future. The results show that the total shallow-groundwater recharge is mainly raised by the increases in precipitation infiltration and surface-water irrigation infiltration. Meanwhile, the decrease of groundwater withdrawal contributes to reduce the total discharge. The recharge–discharge structure of local groundwater was still in a negative balance but improved gradually. The shallow-groundwater level in most parts was still falling before 2030, but more slowly. This study can benefit the rational exploitation of water resources in the Haihe River plain.

Technology targeting for sustainable intensification of crop production in the Delta region of Bangladesh

Abstract. Remote sensing data are nowadays being acquired within short intervals and made available at a low cost or for free. This opens up opportunities for new remote sensing applications, such as the characterization of entire regions to identify most suitable areas for technology targeting. Increasing population growth and changing dietary habits in South Asia call for higher cereal production to ensure future food security. In the Delta area of Bangladesh, surface water is considered to be available in quantities large enough to support intensification by adding an irrigated dry season crop. Fuel-efficient, low lift axial flow pumps have shown to be suitable to carry water to fields that are within a buffer of four hundred meters of the rivers. However, information on how and where to target surface water irrigation efforts is currently lacking. We describe the opportunities and constraints encountered in developing a procedure to identify cropland for which axial flow pumps could be successfully deployed upon in a 43’000 km2 area. First, we isolated cropland and waterways using Landsat 5 and 7 scenes using image segmentation followed by classification with the random forest algorithm. Based on Landsat 7 and 8 scenes, we extracted maximum dry season enhanced vegetation index (EVI) values, which we classified into fallow, low-, and high-intensity cropland for the last three years. Last, we investigated the potential for surface water irrigation on fallow and low-intensity land by applying a cropping risk matrix to address the twin threats of soil and water salinity. Our analysis indicates that there are at least 20,000 ha of fallow land under the low-risk category, while more than 100,000 ha of low-intensity cropland can be brought into intensified production. This information will aid in technology targeting for the efficient deployment of surface water irrigation as a tool for intensification.

Arsenic in Rice grains at Sonargaon, Bangladesh

Rice plants absorb substantial amount of arsenic when grown in rice field soil containing 3.21 mg/kg arsenic and irrigated with contaminated groundwater from a shallow tube-well having 476 ± 3 ?g arsenic/l at Sonargaon, Bangladesh. It is revealed that highest total arsenic accumulation occurred in roots (5.790 ± 0.337 mg/kg) followed by shoots (3.766 ± 0.370 mg/kg) and brown-rice grains (2.552 ± 0.507 mg/kg). The concentration of total arsenic in rice grains was beyond permissible limit (1.00 mg/kg) for human consumption. At the time of harvest 4.90 ± 1.11 - 8.27 ± 1.35 mg As/kg soil remained in the rice field soil. However, majority of the soil arsenic is washed out by rain and flood water leaving more than 3.00 mg As/kg soil after flood period which along with high level of As contaminated groundwater for irrigation, elevated the level (up to 8.27 ± 1.35 mg As/kg soil) beyond permissible limit of e.g. in USA it is 5 mg/kg soils for agriculture use. To keep the environment clean, surface water for irrigation has been suggested. DOI: http://dx.doi.org/10.3329/bjb.v44i1.22728 Bangladesh J. Bot. 44(1): 85-89, 2015 (March)

Assessment of surface water irrigation potential in the Ethiopian highlands: The Lake Tana Basin

Although Ethiopia has a large potential to develop surface irrigation, only 5% of the 30 to 70millionhectares (ha) potentially available has been developed. To examine the underlying causes of this lack of irrigation development, this study evaluates the suitability of surface water irrigation for the Lake Tana Basin development corridor. Surface water availability and land potentially suitable for irrigation development were considered. Surface water potential was examined by analyzing long-term daily historical river discharges. Land suitable for irrigation was determined with a GIS-based multi-criteria evaluation, which considers the interaction of various factors such as climate, river proximity, soil type, land cover, topography/slope, and market outlets. The results indicate that nearly 20% of the Lake Tana Basin is suitable for surface irrigation. However, after analyzing 27years of river discharge, less than 3% of the potential irrigable area (or less than 0.25% of the basin area) could be irrigated consistently with runoff from the river systems. Thus, the irrigation potential in the Lake Tana Basin can be met by increasing dry season flows, by improving upland infiltration, by supplying water from reservoirs, or by pumping water directly from Lake Tana.

Phosphorus losses from an irrigated watershed in the northwestern United States: case study of the upper snake rock watershed.

Watersheds using surface water for irrigation often return a portion of the water to a water body. This irrigation return flow often includes sediment and nutrients that reduce the quality of the receiving water body. Research in the 82,000-ha Upper Snake Rock (USR) watershed from 2005 to 2008 showed that, on average, water diverted from the Snake River annually supplied 547 kg ha of total suspended solids (TSS), 1.1 kg ha of total P (TP), and 0.50 kg ha of dissolved P (DP) to the irrigation tract. Irrigation return flow from the USR watershed contributed 414 kg ha of TSS, 0.71 kg ha of TP, and 0.32 kg ha of DP back to the Snake River. Significantly more TP flowed into the watershed than returned to the Snake River, whereas there was no significant difference between inflow and return flow loads for TSS and DP. Average TSS and TP concentrations in return flow were 71 and 0.12 mg L, respectively, which exceeded the TMDL limits of 52 mg L TSS and 0.075 mg L TP set for this section of the Snake River. Monitoring inflow and outflow for five water quality ponds constructed to reduce sediment and P losses from the watershed showed that TSS concentrations were reduced 36 to 75%, but DP concentrations were reduced only 7 to 16%. This research showed that continued implementation of conservation practices should result in irrigation return flow from the USR watershed meeting the total maximum daily load limits for the Snake River.

Chemical Quality of Surface Water of Bhola Sadar Upazila in Bangladesh for Irrigation, Aquaculture, Drinking and Livestock Consumption

A study was carried out with 25 pond water samples of Bhola Sadar Upazila to assess the quality of surface water for irrigation, aquaculture, drinking and livestock consumption. Chemical analyses of different parameters were done to assess the quality of water. All of the water samples showed slightly acidic in nature. Sixteen surface water samples were not suitable for drinking and aquaculture in respect of pH (pH <6.5). Electrical conductivity (EC) categorized the waters as “low salinity” (C1) to “medium salinity” (C2) class for irrigation. With respect to total dissolved solids surface waters were within “highest desirable limit” for drinking and irrigation and suitable for livestock consumption and aquaculture. Calcium and Magnesium content rated the samples as “maximum permissible” and “highest desirable” limit for drinking. All the samples were suitable for drinking in case of Na and K, 21 samples were not suitable for aquaculture due to higher (>5.0 mg L-1) K content. Six samples were unsuitable for livestock due to higher (Cl >30mgL- 1) Cl values. SSP rated 9 samples as “good”, 1 as “excellent”, 6 as “doubtful” and 9 as “permissible” for irrigation. With respect to RSC 21 samples were “suitable”, 3 were “marginal” and 1 was “unsuitable” for irrigation. Hardness classified 14 samples within “moderately hard”, 10 within “soft” and only one as “hard” limit for irrigation and 1 sample (No. 16) was unsuitable for livestock consumption. P, B, Cu and As concentration categorized all the samples suitable for irrigation, aquaculture, drinking and livestock consumption.DOI: http://dx.doi.org/10.3329/jesnr.v6i1.22053 J. Environ. Sci. & Natural Resources, 6(1): 131-140 2013

Impact of Conjunctive Use of Water Resources on Crop Production in Canal Command Area-A Case Study

The study is carried out for Jamuniya, Jhansi and Khulri Minor of Left Bank Canal network of Rani Avanti Bai Sagar irrigation project. It constitutes impact of conjunctive use on water resource utilization pattern, irrigation depth, changes in cropping pattern, effect on yield of crops, water table depth and net farm return. The results indicated in Jamuniya minor have the use of surface water for irrigation is more than ground water in last 10 years. In Jhansi minor, the use of surface water for irrigation was maximum in year 2001–02 (114.88 ha) and then continuously decreased during last 10 years reached to 50.55 ha. Reverse trend was observed in Jhansi minor with use of ground water for irrigation and similar pattern was found in Khulri minor. The depth of irrigation for wheat, gram and green pea was observed the highest in Jhansi head reach 26.5 cm, 10.6 cm and 25.8 cm, respectively and the lowest in Khulri middle reach as 12.5 cm, 5.0 cm and 15.0 cm for wheat, gram and green pea, respectively. The wheat area intensity continuously increased in all minors during 2003–04 to 2009–10. The yield of wheat registered the highest (38 q/ha) in head reach of Jamuniya minor and the lowest (27.7 q/ha) in middle reach of Jamuniya minor. The yield of gram was maximum (18.21 q/ha) in tail reach of Jhansi minor and minimum (14.0 q/ha) in middle reach of Khulri minor.

Cause Analysis and Prediction of the Groundwater Level in Jinghuiqu Irrigation District

Groundwater environment evolution can comprehensively reflect groundwater dynamics. Based on the relationship between the groundwater system and the external environment in Jinghuiqu irrigation district, adopting the Principal Component Analysis method, variation characteristics of environmental factors including climate and human activity and their impact on groundwater were systematically analyzed. The results show that groundwater level in Jinghuiqu irrigation district has been significantly dropped in nearly 34 years; the reduction of surface water irrigation use, which reduced the amounts of groundwater recharge and destroyed the water balance, is considered as the most direct cause for falling of regional groundwater level. Besides, reduction in precipitation, increase of evaporation also accelerated the declining of the groundwater level at some extent. Finally, a predicting method of groundwater depth based on BP neural network is developed. The experimental results show that the predicting model can reasonablely predict the groundwater level in Jinghuiqu irrigation district with a high precision.

Is irrigation water price an effective leverage for water management? An empirical study in the middle reaches of the Heihe River basin

Serious water scarcity, low water-use efficiency, and over-exploitation of underground water have hindered socio-economic development and led to environmental degradation in the Heihe River basin, northwestern China. Price leveraging is an important tool in water demand management, and it is considered to be effective in promoting water conservation and improving water use efficiency on the premise that water demand is elastic. In the present study, we examine whether price is an effective and applicable instrument for restraining the increasing demand for agricultural irrigation water in the middle reaches of the Heihe River basin and how will it affect farmers’ decisions on irrigation and crop structure. Specifically, the price elasticity of agricultural water demand was estimated based on the irrigation water demand function. The results show that the agricultural irrigation water price is statistically significant, but its elasticity is very low under current low water price. Price leverage cannot play a significant role in the context of the current pricing regime and farmers’ response to price increase is intrinsically weak. To create incentives for conserving water and improving irrigation efficiency, price mechanism should be accompanied with clearly defined and legally enforceable water rights, restricted water quota measures, and reform of water authorities and water-user associations. Furthermore, increases of surface irrigation water price may lead to the over-withdrawal of groundwater, consequently, effective groundwater licensing and levying must take place to limit the total volume of groundwater withdrawal. In all, improving irrigation efficiency through better management and the adoption of water-saving technologies is the ultimate way to deal with the challenges facing irrigated agriculture in the middle reaches of the Heihe River basin.