Conjunctive Water Research Articles

Nonlinear Optimisation Using Production Functions to Estimate Economic Benefit of Conjunctive Water Use for Multicrop Production

Uncertainty and shortages of surface water supplies, as a result of global climate change, necessitate development of groundwater in many canal commands. Groundwater can be expensive to pump, but provides a reliable supply if managed sustainably. Groundwater can be used optimally in conjunction with surface water supplies. The use of such conjunctive systems can significantly decrease the risk associated with a stochastic availability of surface water supply. However, increasing pumping cost due to groundwater drawdown and energy prices are key concerns. We propose an innovative nonlinear programing model for the optimisation of profitability and productivity in an irrigation command area, with conjunctive water use options. The model, rather than using exogenous yields and gross margins, uses crop water production and profit functions to endogenously determine yields and water uses, and associated gross margins, respectively, for various conjunctive water use options. The model allows the estimation of the potential economic benefits of conjunctive water use and derives an optimal use of regional level land and water resources by maximising the net benefits and water productivity under various physical and economic constraints, including escalating energy prices. The proposed model is applied to the Coleambally Irrigation Area (CIA) in southeastern Australia to explore potential of conjunctive water use and evaluate economic implication of increasing energy prices. The results show that optimal conjunctive water use can offer significant economic benefit especially at low levels of surface water allocation and pumping cost. The results show that conjunctive water use potentially generates additional AUD 57.3 million if groundwater price is the same as surface water price. The benefit decreases significantly with increasing pumping cost.

Groundwater as an emergency source for drought mitigation in the Crocodile River catchment, South Africa

Abstract. Global climate change has received much attention worldwide in the scientific as well as in the political community, indicating that changes in precipitation, extreme droughts and floods may increasingly threaten many regions. Drought is a natural phenomenon that causes social, economical and environmental damage to society. In this study, we assess the drought intensity and severity and the groundwater potential to be used as a supplementary source of water to mitigate drought impacts in the Crocodile River catchment, a water-stressed sub-catchment of the Incomati River catchment in South Africa. The research methodology consists of three parts. First, the spatial and temporal variation of the meteorological and hydrological drought severity and intensity over the catchment were evaluated. The Standardized Precipitation Index (SPI) was used to analyse the meteorological drought and the Standardized Runoff Index (SRI) was used for the hydrological drought. Second, the water deficit in the catchment during the drought period was computed using a simple water balance method. Finally, a groundwater model was constructed in order to assess the feasibility of using groundwater as an emergency source for drought impact mitigation. Results show that the low-rainfall areas are more vulnerable to severe meteorological droughts (lower and upper crocodile). Moreover, the most water stressed sub-catchments with high level of water uses but limited storage, such as the Kaap located in the middle catchment and the Lower Crocodile sub-catchments, are more vulnerable to severe hydrological droughts. The analysis of the potential groundwater use during droughts showed that a deficit of 97 Mm3 yr−1 could be supplied from groundwater without considerable adverse impacts on the river base flow and groundwater storage. Abstraction simulations for different scenarios of extremely severe droughts reveal that it is possible to use groundwater to cope with the droughts in the catchment. However, local groundwater exploitation in Nelspruit and White River sub-catchment will cause large drawdowns (> 10 m) and high base flow reduction (> 20%). This case study shows that conjunctive water management of groundwater and surface water resources is necessary to mitigate the impacts of droughts.

Analysis of spatial\u2013temporal patterns of water table change as a tool for conjunctive water management in the Upper Central Plain of the Chao Phraya River Basin, Thailand

A sustainable strategy for conjunctive water management must include information on the temporal and spatial availability of this natural resource. Because of water shortages in the dry seasons, farmers on the Upper Plain of the Chao Phraya River basin, Thailand, are increasingly using groundwater to meet their irrigation needs. To evaluate the possibilities of conjunctive water management in the area, the spatial–temporal changes in the water table of the Younger Terrace Aquifer were investigated. First, a regional geomorphological map based on field surveys, remote sensing and previous environmental studies was developed. Then, the well data were analyzed in relation to rainfall, streamflow, yield and pumpage, and the data were interpolated using geostatistical techniques. The results were analyzed via integrated zoning based on color theory as applied to multivariate visualization. The analysis results indicate areas that would be more suitable for groundwater extraction in a conjunctive management framework with regard to the natural hydrogeological processes and the effects of human interaction. The kriging results were compared with the geomorphological map, and the geomorphological areas exhibit distinct hydrogeological patterns. The western fans exhibit the best potential for the expansion of conjunctive use, whereas the borders of the northern fans exhibit the lowest potential.

Climate-smart tank irrigation: A multi-year analysis of improved conjunctive water use under high rainfall variability

Although water harvesting is receiving renewed attention as a strategy to cope with increasing seasonal and inter-annual rainfall variability, many centuries-old local water-harvesting reservoirs (tanks) in India are rapidly deteriorating. Easy access to groundwater is seen as one of the major threats to their maintenance and functioning. Potentially, however, conjunctive use of water from rain, tanks and groundwater reserves, supported by proper monitoring, could improve the resilience and productivity of traditional tank irrigation systems. To date, few quantitative multi-annual analyses of such climate-smart systems have been published. To redress this, we assess the sustainability of a rehabilitated tank irrigation system, by monitoring all inputs and outputs over a period of six years (12 cropping seasons). Our results show that during the period considered, improved conjunctive use resulted in a more stable cropping intensity, increased economic water productivity and higher net agricultural income. Groundwater tables were not negatively affected. We argue that improved conjunctive use can considerably reduce the vulnerability of tank irrigation to rainfall variability and thus is a valuable strategy in light of future climate change.

Mitigating Socio-Economic-Environmental Impacts During Drought Periods by Optimizing the Conjunctive Management of Water Resources

Multi-period optimization of conjunctive water management can utilize reservoirs and aquifer carry-over to alleviate drought impacts. Stakeholders’ socio-economic and environmental indices can be used to minimize the socio-economic and environmental costs associated with water shortages in drought periods. The knowledge gap here is the evaluation and inclusion of the socio-economic and environmental value of conjunctive water management in terms of its drought mitigation capability. In this paper, an integrated water quantity-quality optimization model that considers socio-economic and environmental indices is developed. The model considers and integrates reservoir and aquifer carry-over, river-aquifer interaction and water quality with stakeholders’ socio-economic indices of production, net income and labor force employment to evaluate the socio-economic and environmental value of conjunctive water management. Total dissolved solid (TDS) is used as the water quality index for environmental assessments. The model is formulated as a multi-period nonlinear optimization model, with analysis determining the optimal decisions for reservoir release and withdrawal from the river and aquifer in different months to maximize the socio-economic indices of stakeholders within the environmental constraints. The proposed model is used in Zayandehrood water resource system in Iran, which suffers from water supply and pollution problems. Model analysis results show that conjunctive water use in the Zayandehrood water basin reduces salinity by 50 % in the wetland and keeps water supply reduction during a drought under 10 % of irrigation demand.

Modeling Conjunctive Water Use as a Reciprocal Externality

AbstractA reciprocal externality is created in the conjunctive use of hydrologically connected surface and ground water. Hydrologic and economic modeling are integrated to conduct basin‐wide cost benefit analysis to address the market failure of reciprocal conjunctive use externalities. An n‐node partial equilibrium model was formulated in which economic equilibrium was defined by a system of complementary slackness equations. The general model was applied to a three‐node example of a ground water pumper that enjoys the positive externality of canal seepage while inflicting a negative externality of pumping‐induced seepage upon a canal water user. Exogenous demand, supply, and canal conveyance variables were parameterized using site‐specific functional forms and data. The example was solved using mixed complementary programming for the endogenous equilibrium water prices which in turn were used to calculate consumer and producer surplus in the respective surface and ground water markets. A Pigouvian tax/subsidy policy was contrasted against two real‐world policies; eliminating the externality through conservation infrastructure and aquifer recharge. The Pigouvian tax/subsidy aligns prices to erase the wedge between social and private costs. The reciprocal externality produces feedback between the surface and ground water markets that reinforces or cancels the tax/subsidy effect. The recharge payment prices canal seepage via a payment from pumper to canal user that matches the decrease in total pumping cost attributable to the seepage resulting from canal diversion. The Pigouvian tax/subsidy yielded the highest social welfare, followed by the aquifer recharge payment. Conserving water by lining the leaky canal decreased social welfare.

Conjunctive Water Management in the Fixed Rotational Canal System: A Case Study from Punjab Pakistan

In the fixed rotational irrigation system of Pakistan, canal water supplies are usually deficient to meet crop water requirements. Therefore groundwater is widely used to supplement surface supplies. In most of the canal command areas, groundwater is used in conjunction with the surface water to decrease the salinity of irrigation water in an attempt to avoid soil salinization. However, conjunctive use of surface water and groundwater is equally practiced in head and tail ends of the canal system. This results in rising groundwater tables leading to waterlogging in the upstream areas and aggravating salinity problems in the tail areas due to less canal water availability and the poor quality of the groundwater. Therefore strategies need to be developed for surface and groundwater use in such a way that equity in availability of water of acceptable quality is ensured all along the channel. This paper suggests three options to achieve this objective; (1) development of guidelines for proper mixing ratios of surface water and groundwater to maintain acceptable salinity levels; (2) revisiting canal water allocations to provide more canal water to tail-end farmers due to poor quality of groundwater whereas encouraging head farmers to extract more groundwater to meet their demands; and (3) facilitating farmers to develop on-farm storage ponds to store their meager share of canal water and use it through high efficiency irrigation systems such as drip and sprinkler. All these options would require necessary changes in the government policies, institutional arrangements and wide scale dialogue with farmers. For this purpose, network of existing water user associations may play a vital role.

Conjunctive Water Use in Confined Basalt Aquifers: An Evaluation Using Geochemistry, a Numerical Model, and Historical Water Level

As withdrawals from deep compartmentalized aquifers increasingly exceed recharge throughout the western United States, conjunctive water use management alternatives have become an applied research priority. This study highlights both details and limitations of the role of irrigation canal seepage as groundwater recharge, revealing the regional limitations of canal seepage as a dependable source of recharge in overdrawn aquifers. A suite of geochemical indicators were used together with a numerical model to evaluate current and future management scenarios focused on recharge derived from seepage from a region-wide irrigation canal system. Twenty-five years of static groundwater level data were used to relate spatial trends determined using geochemistry and groundwater modeling with “on-the-ground” management practices, which vary based on acreage, crop, and irrigation scheduling. Increasing groundwater age determined using isotope analysis, and declines in potentiometric heads, each correlate with increasing distance from the canal reaches. Predictive modeling indicates that if pumping is gradually reduced, as has been suggested by management agencies, that recharge from canal seepage will be negligible by 2035 due to regional groundwater through-flow and the pattern of potentiometric head recovery. Unfortunately, historic hydrographs suggest that under current groundwater development conditions most wells are not sustainable, irrespective of proximity to the canal.

A multi-period optimization model for conjunctive surface water–ground water use via aquifer storage and recovery in Corpus Christi, Texas

The present study develops and evaluates a decision support system for the conjunctive management of the current surface and proposed aquifer storage and recovery (ASR) facility of the city of Corpus Christi, TX using a simulation–optimization approach. The objective of the model is to maximize water storage in the surface and subsurface storage units while meeting (1) the freshwater inflow requirements to the Corpus Christi estuary and (2) the water demands of the city and its service area. The model is parameterized using streamflow data from the U. S. Geological Survey gauging stations on the Nueces River and its tributaries as well as long-term climatic data and regional hydrogeologic information. Results indicate that a single-well field ASR facility is capable of storing approximately 925 ha-m (7,500 ac-ft) of water over a 5-year period in the Evangeline Aquifer with a total potential storage of about 2,715 ha-m (22,000 ac-ft) of water over the jurisdictional area of the Corpus Christi Aquifer Storage and Recovery Conservation District. Surplus surface water sources are seen to contribute approximately 49–96 % of the water stored in the ASR during the simulation period. The remaining storage came from either Choke Canyon Reservoir or Lake Corpus Christi, which also resulted in a slight reduction in evapotranspiration in both reservoirs. The analysis indicates that the proposed ASR system is not limited on the supply side but multiple well fields may be required to increase the storage capacity within the aquifer.

Optimum management of cyclic storage systems: A simulation–optimization approach

A semidistributed system dynamics simulation model was coupled with a genetic algorithm to develop a novel simulation–optimization approach for conjunctive water use management. The proposed simulation–optimization method uses the concept of cyclic storage systems as a framework to solve conjunctive use problems. As a highly sophisticated conjunctive use template, a cyclic storage system includes two major subsystems: surface water and groundwater. In this research, the dynamic behavior of a cyclic storage system was simulated using system dynamics methodology. The real‐world case study chosen was Kineh Vars Reservoir and its irrigating area, located downstream of the Abhar Rud watershed in west‐central Iran. Operating rules for the system were optimized to satisfy water demands over a planning period of 40 seasons, minimizing the total costs of system construction, operation, maintenance, and elements replacement.

Time series analyses of mean monthly rainfall for drought management in Sokoto, Nigeria

This paper analyses the time series characteristics of rainfall data for Sokoto metropolis for 40 years with a view to understanding drought management. Data for this study was obtained from the Nigeria Metrological Agency (NIMET), Sokoto Airport; Sokoto. The data was subjected to time series tests (trend, cycle, seasonal and decomposition analyses) using additive and multiplicative modeling approach. The results showed an increasing trend of rainfall amount over the metropolis within the period under review. Analysis of seasonality in monthly precipitation showed a concentration of rainfall in the months of June, July and August while it decreases in September; however, the months of March, April, and October do experience some showers of rainfall sometimes. Obviously, result of the seasonality analysis showed that January, February, March, April, May, November and December are dry months. This implies that growing season in Sokoto do end around September. The implication is that farmers in the study area need to stream line their farming activities with a view to making effective use of the available rainfall. The paper also suggests a need for building micro dams, developed underground water resources and or adopts conjunctive water management as part of drought management efforts.Keywords: Rainfall, seasonality, cycle, decomposition, multiplicative modeling, drought

Extraction of Optimal Operation Rules in an Aquifer-Dam System: Genetic Programming Approach

Surface water and groundwater are two important resources that can be used simultaneously to meet demand. To sustain these resources in a planning horizon, different conditions of supply and demand can be balanced by operational rules. Those rules can be extracted from prior experience while operating a conjunctive water system and then applied in future periods. Genetic algorithm (GA) is an evolutionary algorithm that has been extensively used to determine optimal operation rules. Commonly, the operation rule pattern is fixed by a linear equation, and GA calculates optimal coefficients in a defined pattern. In this paper, to compute a more effective operation rule that yields a better objective function value compared to GA for the same conditions, a fixed-length gene genetic programming (FLGGP) rule is developed and extracted based on genetic programming (GP). The FLGGP rules are employed in an aquifer-dam system with two subsystems, in which each subsystem can supply parts of the demand. Results show that the obtained objective function value using the FLGGP rules is 26 percent better compared to the common linear rule by GA. The developed operational rule uses more functions and mathematical operators than numerical variables. Thus, FLGGP is more flexible and effective in determining optimal rule curves for a conjunctive aquifer-dam system.

Integrated Modeling of Conjunctive Water Use in a Canal-Well Irrigation District in the Lower Yellow River Basin, China

AbstractThe Yellow River Basin is a closed basin under serious stress with dense population, intensive agriculture, and excess water withdrawals. Low water use efficiency and groundwater overexploitation are threatening the sustainable development of the basin. This paper describes a coupled modeling approach to analyze sustainable management strategies in surface–groundwater conjunctive use irrigation districts in the lower Yellow River Basin. An appropriate irrigation schedule and an optimal range of groundwater levels are first established using the soil water atmosphere plant (SWAP) model with data from an irrigation experiment station. The integrated surface water and groundwater model was then set up using modified soil and water assessment tool (SWAT2000) and modular three-dimensional groundwater flow model (MODFLOW) models. The two models were connected through standardized simulation grids and calibrated using field measurements. Five scenarios that were designed according to different well-canal...

ANALYSING STRUCTURAL AND NON‐STRUCTURAL OPTIONS TO IMPROVE UTILITY OF IRRIGATION AREAS USING A SYSTEM DYNAMICS APPROACH

ABSTRACTUsing the philosophy of system thinking, this paper conceptualizes the dynamics governing major structural and non‐structural measures for rehabilitation of irrigation networks aimed at improving the irrigation utilities. The dynamics of improvement of irrigation networks is studied, on the basis of indicators such as adequacy, efficiency, equity, flexibility and dependability. In the present paper, the application of system dynamics analysis is demonstrated by applying it to six irrigation areas in Iran to present irrigation causal loop diagrams. The results, specifically for the Qazvin irrigation network, have been documented based on the facts.For the Qazvin irrigation network, system utility not only improves through increase in investment planning, but through conjunctive water management, reducing social constraints, and control of crop patterns and the cultivated area. Reduction of social and legal constraints with change of structural and non‐structural measures to longer‐term sustainable measures is more effective than the other policies. As a conclusion it could be stated that the system dynamics approach can be successfully applied to integrated analysis of irrigation network policy options, as well as to identification of key factors leading to degradation of irrigation networks and how to make effective decisions to sustain system utility over time. Copyright © 2012 John Wiley & Sons, Ltd.

Spatial Climate Variability and Its Impact on Irrigated Hydrology in a Canal Command

Depth to watertable continuously increases from head to tail in most of the canal commands in Punjab, Pakistan, in spite of equitable canal water supplies. In the wake of increased groundwater use with passage of time, the tail end farming community and irrigation management institutions are to confront this emerging issue very prudently. To comprehend this dilemma, canal water availability, crop water requirement and groundwater recharge across the Lower Bari Doab Canal command were analyzed. Annual rainfall decreases towards tail (212 mm) as compared to head (472 mm), in contrary, annual gross and net crop water requirement at tail end are 10.2 and 32.5% higher, respectively, as compared to head end. As a result, groundwater mining is taking place in tail end at 0.34 m/year, whereas in head end areas, the situation is stable. Actually, in tail end areas, groundwater recharge rates are considerably low as compared to the head end. Spatial climate variability across the command is the main cause for these inequities. Reallocation of canal water and/or enhancing recharge to groundwater in these relatively more water stressed areas during wet years needs to be sought, otherwise any groundwater management activity in this regard will not have any technical and social viability. Ignoring climatic variability within the canal command is one of the serious issues in irrigation system design that prevents achieving the optimal level of conjunctive water use and as a result, the highest potential agricultural output cannot be achieved.

Modeling the effects of saline water use in wheat-cultivated lands using the UNSATCHEM model

Waters of poor quality are often used to irrigate crops in arid and semiarid regions, including the Fars Province of southwest Iran. The UNSATCHEM model was first calibrated and validated using field data that were collected to evaluate the use of saline water for the wheat crop. The calibrated and validated model was then employed to study different aspects of the salinization process and the impact of rainfall. The effects of irrigation water quality on the salinization process were evaluated using model simulations, in which irrigation waters of different salinity were used. The salinization process under different practices of conjunctive water use was also studied using simulations. Different practices were evaluated and ranked on the basis of temporal changes in root-zone salinity, which were compared with respect to the sensitivity of wheat to salinity. This ranking was then verified using published field studies evaluating wheat yield data for different practices of conjunctive water use. Next, the effects of the water application rate on the soil salt balance were studied using the UNSATCHEM simulations. The salt balance was affected by the quantity of applied irrigation water and precipitation/dissolution reactions. The results suggested that the less irrigation water is used, the more salts (calcite and gypsum) precipitate from the soil solution. Finally, the model was used to evaluate how the electrical conductivity of irrigation water affects the wheat production while taking into account annual rainfall and its distribution throughout the year. The maximum salinity of the irrigation water supply, which can be safely used in the long term (33 years) without impairing the wheat production, was determined to be 6 dS m−1. Rainfall distribution also plays a major role in determining seasonal soil salinity of the root zone. Winter-concentrated rainfall is more effective in reducing salinity than a similar amount of rainfall distributed throughout autumn, winter, and spring seasons.

Modelo de preferencia multiatributo para la planificación óptima de cultivos de regadío en condiciones de escasez de agua

La sostenibilidad de los recursos hídricos tiene un papel clave en la existencia y durabilidad de los sistemas agrícolas de riego y depende en gran medida de la planificación de los cultivos. El proceso de decisión es complejo, debido a una serie de restricciones y el deseo de asegurar la diversificación de los cultivos y la participación de diversos parámetros afectados. El objetivo del presente estudio fue desarrollar un modelo multicriterio completo para seleccionar una combinación adecuada de cultivo en un distrito de riego con escasez hídrica. La planificación de un sistema óptimo de cultivos en regadíos se realizó considerando once y nueve atributos de decisión para jerarquizar el tipo de cultivo y su porcentaje de superficie, respectivamente. Los resultados indican que el enfoque de preferencia de atributos múltiples puede sintetizar varios conjuntos de criterios en la selección del tipo de cultivo y la superficie cultivada. El análisis de validación muestra que las preferencias generadas por el modelo propuesto están razonablemente de acuerdo con las obtenidas en el modelo de uso del agua. En consecuencia, el modelo podría ser utilizado para agregar preferencias a fin de obtener una decisión de grupo, mejorar la comprensión del problema de elección, adaptarse a múltiples objetivos y aumentar la transparencia y la credibilidad en la toma de decisiones en las que la planificación de cultivos esté involucrada.

Flood‐Pulse Effects on Zooplankton Assemblages in a River‐Floodplain System (Gemenc Floodplain of the Danube, Hungary)

AbstractWe studied the structure and population dynamics of zooplankton assemblages in the water bodies (eu‐, para‐, plesiopotamal and conjunctive water bodies) of a temperate floodplain during flood events. Here we report differences in the species composition of these water bodies in the two stages of flood pulses: rising vs. receding. During the receding period the proportion of larger and tychoplanktonic species increased. Similarity among zooplankton assemblages of these floodplain water bodies increased during the rising and decreased during the receding period. Species richness, diversity and population density values of zooplankton assemblages increased during the receding period in all types of water bodies except the eupotamal. The guild ratio of rotifer assemblages showed characteristic, but somewhat ambiguous changes. We conclude that the hydrological regime affects the structure and dynamics of zooplankton assemblages on the floodplain. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Modeling for conjunctive use irrigation planning in sodic groundwater areas

Prevalent irrigation water quality guidelines for use of sodic groundwater on sandy loam soils of Haryana for kharif (monsoon) fallow–rabi (winter) wheat crop rotation were investigated through modeling with UNSATCHEM. Three sandy loam soils that vary with respect to soil CEC (Cation Exchange Capacity) and Ks (Saturated Hydraulic Conductivity) were considered in the modeling. A procedure was developed to identify safe SAR value for sodic groundwater at a constant RSC for individual farm/soil considering soil CEC and proportions of sodic and fresh waters used for irrigation as variables. The criterion was that if the SAR of available sodic groundwater exceeded the safe SAR-value for irrigation water, a reduction in crop yield occurs. With this assumption, the procedure was tested with published data and the specific data collected from farmers’ fields. If SAR of groundwater exceeds the safe SAR-value, rice–wheat rotation is assumed to be not sustainable in the long-term. The sustainability of rice–wheat crop rotation in sodic groundwater areas in the Assandh and Nissang blocks of the Karnal district of Haryana was assessed. The described procedure of identifying the safe SAR-values for individual farm/soil is more appropriate and flexible than already existing guidelines and could be easily used for efficient conjunctive water use planning of sodic and fresh water.

GIS analysis of conjunctive water resource use in Nganjuk district, east Java, Indonesia

Water shortages during the dry season threaten sustainable agricultural production in Nganjuk District, East Java, Indonesia. To mitigate this problem, farmers adopted conjunctive use of surface water and groundwater, but the sustainability of this practice has not been investigated. This study temporally and spatially assessed water allocation in Nganjuk District when conjunctive irrigation was used. In particular, the land cover, water balance, and irrigation well density (IWD) were analyzed using time series GIS and remote sensing data to obtain their temporal and spatial distributions. First, the land cover was analyzed to determine cropping intensity, and the water balance was analyzed temporally and spatially. IWD was introduced to facilitate the water balance analysis. Second, the land cover, water balance, and IWD results were overlaid. Third, the effectiveness of the IWD method, the magnitude of water shortages, and the sustainability of groundwater resources were considered. Temporal and spatial water shortages in irrigation blocks were observed during the dry season. The change of storage showed a surplus during the wet and early dry seasons and a shortage during the late dry season. The annual water balances indicated that the southern part had a surplus, and the northern part experienced water shortages, especially downstream of the Widas River. Conjunctive use during the late dry season was predominant and concentrated in the southern part (83% of southern blocks). IWD was appropriate for examining groundwater use trends and was effective for expressing average withdrawal data (R 2 = 0.87).