Water Simulation Model Research Articles

Utilization of satellite altimetry retrieved river roughness properties in hydraulic flow modelling of braided river system

ABSTRACT Sand bed braided rivers, such as the Brahmaputra, are highly dynamic in nature. The braided rivers change their course frequently, which causes huge bank erosion and sand bar migration. During the monsoon season the braided river has higher sediment-carrying capacity and the erosion power. A large amount of energy dissipation takes place in terms of river fragmentation and sand bar migration and bar erosion. These are common morphological characteristics within the sand bed braided rivers. The dynamic river bed and planform offer varying resistance to flow based on the hydrologic regime and reach characteristics of the river. Estimation of channel roughness coefficient is important for hydraulic modelling of the river. In this study, roughness characteristics of the Brahmaputra river were estimated using altimetry derived river stage records at different reaches of the river. The estimated Manning's roughness coefficients were incorporated in one-dimensional hydraulic model to perform simulations over the middle reach of the Brahmaputra River. Comparison of seasonal water level differences at different reaches of the river was performed using altimetry retrieved and model simulated water level for 2014 and 2015, respectively. The simulated water levels from altimetry derived Manning's roughness coefficient were found to be in close range with altimetry retrieved water levels for 2014 and 2015. It was found that the spatio-temporal variation of Manning's roughness coefficient proved to be an important parameter for modelling braided river systems such as the Brahmaputra.

Modeling hydrological response to land use/cover change: case study of Chirah Watershed (Soan River), Pakistan

Assessment of land use change impacts on watershed hydrologic processes is of great importance to draw the attention of water resource managers and policy makers for better planning and management of the shrinking resources for the survival of surrounding population of the region. Chirah watershed is an important hydrologic unit which generates an average of 0.53 MCM water per day. Soan River originates from here, supplying an average inflow of 0.2 MCM day−1 to Simly Dam. Since a couple of decades, rainfall variability coupled with growing population is threatening Soan River flows. Deforestation and land use/land cover (LULC) changes have affected the natural pathways of water, decreased groundwater recharge, and triggered flash floods. Therefore, the aim of this research was to assess the impact of LULC changes on the hydrologic processes of the watershed using the Soil and Water Assessment Tool (SWAT), a hydrological model to propose management strategies. LULC change assessment was carried out on Landsat-5 TM and OLI_TIRS images through ‘Supervised Classification’ at four-time steps (1990, 1999, 2010, and 2016). Due to limited ground observations, corresponding Google Earth images were used in mapping. The SWAT model was evaluated using the Nash-Sutcliffe efficiency (NSE) and relative volumetric error (RVE) objective functions on monthly time steps. The NSE achieved during calibration and validation, 0.63 and 0.45, respectively, indicates acceptable levels of model performance despite outliers in the hydro-meteorological dataset. Similarly, the RVE was less than ±5% during both periods, indicating that the model simulated water balance reasonably well. Changes in LULC resulted in alteration of all the hydrological parameters. Conversion of scrub thorny forest (14.74%) into built-up areas (9%) resulted in higher imperviousness which triggered runoff to 24% and lowered groundwater recharge by 8% in 27 years indicating that the hydrologic regime is sensitive to LULC changes.

An In-Depth Assessment of Water Resource Responses to Regional Development Policies Using Hydrological Variation Analysis and System Dynamics Modeling

To maintain sustainability and availability of regional water resources, appropriate integrated water resource management (IWRM) should be based on an assessment of water resource background and responses to regional development and utilization policies. The study proposed an assessment method combining hydrological variation analysis with a system dynamics (SD) model to support IWRM in the Baiyangdian Region, Northern China. Integrated variation analysis and attributive analysis were used to identify variation time and causes of runoff. Then, based on the current water resource situation, an accessibility analysis examined the possibility of achieving a water resources supply and demand balance of social economic development and the ecological environment within individual internal management. Finally, an SD model simulated water resource response to development policies to predict future policy impacts. Results showed that 65.18% of the impact on runoff was from human activities. Sustainability goals were impossible through internal management, but with eco-migration policies and 1 × 108 m3 inter-basin transferred water, it could quickly be achieved, and water ecosystem function could also be recovered. Establishment of the Xiong’an New Area necessitated introduction of integrated cross-basin management to protect the Baiyangdian Region from degradation of its ecological function. Our study proposed a new method for comparation of internal and cross-basin IWRM.

Meeting agricultural and environmental water demand in endorheic irrigated river basins: A simulation-optimization approach applied to the Urmia Lake basin in Iran

Competition for water between agriculture and the environment is a growing problem in irrigated regions across the globe, especially in endorheic basins with downstream freshwater lakes impacted by upstream irrigation withdrawals. This study presents and applies a novel simulation-optimization (SO) approach for identifying water management strategies in such settings. Our approach combines three key features for increased exploration of strategies. First, minimum environmental flow requirements are treated as a decision variable in the optimization model, yielding more flexibility than existing approaches that either treat it as a precomputed constraint or as an objective to be maximized. Second, conjunctive use is included as a management option by using dynamically coupled surface water (WEAP) and groundwater (MODFLOW) simulation models. Third, multi-objective optimization is used to yield entire Pareto sets of water management strategies that trade off between meeting environmental and agricultural water demand. The methodology is applied to the irrigated Miyandoab Plain, located upstream of endorheic Lake Urmia in Northwestern Iran. Results identify multiple strategies, i.e., combinations of minimum environmental flow requirements, deficit irrigation, and crop selection, that simultaneously increase environmental flow (up to 16 %) and agricultural profit (up to 24 %) compared to historical conditions. Results further show that significant temporary drops in agricultural profit occur during droughts when long-term profit is maximized, but that this can be avoided by increasing groundwater pumping capacity and temporarily reducing the lake’s minimum environmental flow requirements. Such a strategy is feasible during moderate droughts when resulting declines in groundwater and lake water levels fully recover after each drought. Overall, these results demonstrate the usefulness and flexibility of the methodology in identifying a range of potential water management strategies in complex irrigated endorheic basins like the Lake Urmia basin.

Analyzing the effects of past, present, and future water consumption through analog mapping

The average amount of water usage per capita is 70 gallons per day. Individuals do not often consider their daily water consumption. Model simulations are useful in predicting future water consumption scenarios. Simulation models consist of the different relationships of elements and their correspondence to one another. On the other hand, analog mapping is being used more frequently to visually express and examine the differences in data throughout multiple physical geographical locations. In this study we determine the similarities between water usages across various cities. The cities that are compared are along the continental United States of America regardless of their climate variability. Historical water usage from 50 years ago, water usage habits as the current phenomenon, and projected water usage scenarios in a future 50 years from now are carefully analyzed. This study combines water usage predictions along with analog mapping to evaluate water‐availability and water‐usage. Results from this study can be used to assess the impact of unregulated water usage and the risks of water depletion. The interconnection of both water simulation models as well as analog mapping can help prompt distinct water usage perspectives in addition to alternative methods of communication. Further research can help evaluate alternative development scenarios.Support or Funding InformationNSF LEAP Scholars Program

Method to Assess Climate Change Impacts on Hydrologic Boundaries of Individual Wetlands

Potential impacts of climate change on the position of the wetland-hydrology boundary were estimated for four sites in the Eastern U.S. Precipitation and temperature predictions were obtained from the Hadley general circulation model (UKMO-HadCM3) because it most closely approximated observed precipitation for the period 1950–2000. The DRAINMOD hydrologic model was used to compute daily water table levels over two time periods: 1983–2012 (current conditions) and 2041–2070 (future conditions). For each site and time period, the model simulated water table depths for a soil pedon (Typic Paleaquult) that previous work demonstrated was on the wetland-hydrology boundary. Results for the Pitt County site in NC showed that by 2070 the wetland-hydrology boundary would have moved “downhill” to a point that was approximately 17 cm lower in elevation than where the boundary was in 2012 due to a 20% increase in evapotranspiration. Similar analyses were done for hypothetical wetland soils in Miami FL, Easton MD, and Portland ME where the wetland hydrology boundaries were estimated to drop in elevation by 5, 10 and 25 cm, respectively. Our results demonstrated that climate change may have significant impact on wetland boundaries.

Evaluating the transferability of monthly water balance models under changing climate conditions

ABSTRACTMonthly water balance models (MWBMs) are often used for making flow projections under climate change. As such, these models should provide accurate flow simulations; however, they are seldom evaluated in this regard. This paper presents a comprehensive framework intended for the evaluation of the applicability of MWBMs under changing climatic conditions. The framework consists of analyses of consistency in model performance, parameter estimates and simulated water balance components, and a subjective assessment of model transferability. Four MWBMs – abcd, Budyko, GR2M and WASMOD – are used to simulate runoff in the Wimmera catchment affected by the Millennium drought. Although abcd and Budyko slightly outperformed GR2M and WASMOD, none of the models performed well in transfer to the driest period. The greatest variability is detected in simulated groundwater storage and baseflow; thus, these model components should be improved and/or enhanced calibration strategies should be employed to advance the transferability of MWBMs under changing climate.

A LISFLOOD-FP hydraulic model of the middle reach of the Congo

In this paper we attempt to produce a first hydrodynamic model of the middle reach of the Congo river system in order to understand what controls this river’s unique bimodal flood pulse. The model covers the area between Kisangani and Kinshasa on the main stem and includes the major tributaries and the Cuvette Centrale wetland, one of the world’s largest and most understudied lowland regions. A mixture of in-situ discharges and modelled discharge from a basin-wide catchment hydrology model were used to force a four-kilometre resolution hydrodynamic simulation developed using the LISFLOOD-FP model. River channels are represented as sub-grid scale features and their width is therefore decoupled from that of the over-lying floodplain grid. Unknown channel friction and bathymetry parameters were calibrated using ERS-2 and Envisat satellite altimetry measurements of channel water level. The calibrated model simulated channel water surface elevations across the domain with a bias and root mean square error of 0.185 and 0.842 m respectively. The value for root mean squared error is close to that obtained for comparisons of ERS-2 and Envisat satellite altimetry to in-situ water elevation data in similar basins (0.79 m and 0.47 m respectively). The model results imply that the bimodal annual pattern of Congo river discharge is predominantly a hydrological rather than hydraulically-controlled feature, with the channel-floodplain interactions and river constrictions having only a modest impact on the flood wave propagation. Nevertheless, and counter to current understanding, we find that interactions between channels and floodplains do however occur extensively, with over 2100 km of the 13,000 km of channel network in the model identified as zones where water is actively exchanged between channels and floodplains. Whilst the water volume that is exchanged with the floodplain is substantially less than for other large rivers, our results imply that channel-floodplain interactions are a significant feature of Congo flood wave propagation. Overall the model provides insights into the hydraulics of this understudied system that can next be tested both in the field and through more detailed modelling studies.

Increasing Groundwater Availability and Seasonal Base Flow Through Agricultural Managed Aquifer Recharge in an Irrigated Basin

AbstractGroundwater aquifers provide an important “insurance” against climate variability. Due to prolonged droughts and/or irrigation demands, groundwater exploitation results in significant groundwater storage depletion. Managed aquifer recharge (MAR) is a promising management practice that intentionally places or retains more water in groundwater aquifers than would otherwise naturally occur. In this study, we examine the possibility of using large irrigated agricultural areas as potential MAR locations (Ag‐MAR). Using the California Central Valley Groundwater‐Surface Water Simulation Model we tested four different agricultural recharge land distributions, two streamflow diversion locations, eight recharge target amounts, and five recharge timings. These scenarios allowed a systematic evaluation of Ag‐MAR on changes in regional, long‐term groundwater storage, streamflow, and groundwater levels. The results show that overall availability of stream water for recharge is critical for Ag‐MAR systems. If stream water availability is limited, longer recharge periods at lower diversion rates allow diverting larger volumes and more efficient recharge compared to shorter diversion periods with higher rates. The recharged stream water increases both groundwater storage and net groundwater contributions to streamflow. During the first decades of Ag‐MAR operation, the diverted water contributed mainly to groundwater storage. After 80 years of Ag‐MAR operation about 34% of the overall diverted water remained in groundwater storage while 66% discharged back to streams, enhancing base flow during months with no recharge diversions. Groundwater level rise is shown to vary with the spatial and temporal distribution of Ag‐MAR. Overall, Ag‐MAR is shown to provide long‐term benefits for water availability, in groundwater and in streams.

Application of satellite altimetry in understanding river–wetland flow interactions of Kosi river

Flood-plain wetlands are the seasonal water bodies formed along a river. These wetlands become active during the monsoon season, which frequently grow in size with seasonal floods and eventually dry up during the non-monsoon season. The flow interaction between flood-plain wetlands and the river sometimes vary over a very short period in response to rapid rise in the river water level due to high precipitation in its upstream catchment. Understanding the complex flow interactions between the river and its associated flood-plain wetlands with field-based measurements of wetland hydrologic characteristics is always a challenging task. To overcome these challenges, an attempt has been made to utilise Topex/Poseidon satellite altimetry-derived water levels into a hydrodynamic model (HEC-RAS) to study river and wetland flow interactions in the lower reach of the Kosi river in India. The satellite altimetry-derived water levels and Landsat satellite images on the Kosi wetlands are used to develop volume-elevation relation. HEC-RAS is setup over the study area and calibrated for different values of manning’s roughness coefficient (n) for the river bank and the main channel of the river for the period of 1993–1996. Unsteady flow simulations are carried out for different monsoon seasons to simulate daily river flow interaction (inflow/outflow) between river and wetlands. Statistical analysis is performed between the altimetry-derived and the model-simulated water levels. It is found that simulated water levels are in good agreement ( $$R^{2}=0.87$$ , root mean square error of 0.84 m and Nash–Sutcliffe efficiency coefficient of 0.85) with altimetry-derived water levels. The analysis of simulations indicates that interactions between the wetland and the river are bidirectional with most of the flow coming out from the river during the month of August and leaving out from the wetlands during the month of September. The wetlands respond in three different ways, i.e., (i) gaining stage, (ii) wetland and river in equilibrium and (iii) loosing stage, which is reflected on water levels of the river and wetland. This study demonstrates complex interaction processes happening between the Kosi river and its surrounding wetlands.

A surrogate-based simulation–optimization approach application to parameters’ identification for the HydroGeoSphere model

A systematic approach is needed to use water more productively, because water shortages limit socio-economic development in many parts of the world. The aim of this paper is to establish a surrogate-based simulation–optimization approach to identify parameter values for a fully integrated surface water and groundwater flow coupling simulation. A surface water and groundwater flow coupling simulation model was implemented using HydroGeoSphere (HGS) model and the parameter sensitivities in the model were analyzed using local sensitivity analysis method. The parameters that exerted a large influence on the output results of the HGS model were then selected as stochastic variables, and the stochastic variable data sets were generated using the latin hypercube sampling (LHS) method, which, thereby, were used as inputs in HGS model to obtain the corresponding outputs. On the basis of input and output data sets, a kriging surrogate model of the HGS model was then established and verified, and parameter values of HGS model were identified using a surrogate-based simulation–optimization approach. The results of this study show that parameters that exert a large influence on the simulation output results include hydraulic conductivity, porosity, the van genuchten parameter ( $$\alpha$$ ), and channel manning coefficient. The established kriging surrogate model is an ideal alternative to the HGS model for simulating and predicting, while optimal parameter values can be identified effectively and accurately using the established approach. The results of this research reveal that huge computational loads can be mitigated while using the kriging surrogate as an alternative for a simulation model in the solution process of optimization model.

Approaches for Estimating Soil Water Retention Curves at Various Bulk Densities With the Extended Van Genuchten Model

AbstractSoil bulk density (ρb) variations influence soil hydraulic properties, such as the water retention curve (WRC), but they are usually ignored in soil water simulation models. We extend the van Genuchten WRC model parameters to account for ρb variations using a series of empirical expressions. WRC measurements made on eight soils with various ρb, and textures are used to calibrate these ρb‐related empirical equations. Accordingly, two approaches are developed to estimate WRCs of soils at various ρb. Another eight soils with a wide range of ρb and textures are used to evaluate the accuracy of the new approaches. Approach 1 estimates WRCs for each soil at various ρb using a WRC measurement made at a reference ρb and the soil texture fractions. This approach gives reasonable WRC estimates for the eight validation soils, with an average root‐mean‐square error (RMSE) of 0.025 m3/m3 and an average determination coefficient (R2) of 0.94. For Approach 2, a WRC measurement made at a reference ρb and one additional water content‐matric potential value measured at a different ρb value are used, which produces WRC estimates with an average RMSE of 0.017 m3/m3 and an average R2 of 0.97. The methodology used in Approach 2 is also applied to the Brooks and Corey WRC model to obtain accurate and precise WRC estimates. The proposed approaches have the potential to be incorporated into simulation models for estimating soil hydraulic properties that are affected by transient and variable ρb.

A comprehensive evaluation of pedotransfer functions for predicting soil water content in environmental modeling and ecosystem management

Many pedotransfer functions (PTFs) have been developed for predicting the soil water content at different matric potentials. The use of these functions has been encouraged because of the time and work typically required for measuring it, while the PTFs require commonly measured soil properties such as sand, silt, clay, organic matter content, or bulk density for predicting water retention. In addition, several environmental and ecosystem management simulation models such as DRAINMOD, HYDRUS, EPIC, SPAW, and WEPP use PTFs for computing soil hydraulic properties. Because of the increasing use of the PTFs and their effect in many soil water simulation and transport models, this study revised and tested 13 different PTFs for predicting soil water content at −33 and −1500 kPa, values usually known as field capacity and wilting point. Three of these PTFs were derived from tropical soils while the rest were developed with soil samples collected across the United States. These PTFs were evaluated in Chilean soils as an independent dataset and their improvement after calibration was assessed with this new data. The results demonstrate that the PTFs performance depends on the soils used for their development as the estimates showed a significant improvement after calibration. When predicting water content, Rawls et al. (2004) was the best function before calibration (RMSE = 0.08 for −33 and −1500 kPa), while Gupta and Larson (1979) was the best after calibration (RMSE of 0.06 and 0.05, and r2 values of 0.69 and 0.66 at −33 and −1500 kPa, respectively). Nonlinear PTFs performed better than linear PTFs when predicting water content at field capacity. Finally, bulk density proved to be the key variable and can be used as footprint for soils changes through time. Organic matter content was also a significant input but improved the estimates for some specific matric potentials and PTFs.

Water replenishment for ecological flow with an improved water resources allocation model

With rapid urbanization, there will be more conflict between human systems and the river ecological system, and therefore, ecological operations, practices and research must involve the ecological water replenishment of entire river basins with new modeling tools. In this study, based on a water resource allocation and simulation model (WAS), we establish an ecological flow-oriented water resource allocation and simulation framework (E-WAS) by comprehensively considering both ecological flow constraints and ecological flow targets. To control multiple types of water sources and dynamically allocate water resources to replenish ecological water in the river, virtual reservoirs and ecological units are added to the model network. With new water balance equations for virtual reservoirs and ecological units, the E-WAS can simulate the ecological replenishment process in a river basin and can provide a recommended water replenishment scheme that considers optimization principles. The E-WAS was applied in the Pingshan River Basin, Shenzhen, China. Fourteen ecological units and 38 water supply nodes are considered in the model. A water replenishment scheme that used water from 6 reservoirs and reclaimed water from 5 water sewage plants was selected. This scheme significantly increased the satisfactory degree of ecological water demand and efficiently supported the formulation of a control scheme for the water environment of a basin. The E-WAS framework is similar to model plug-ins but helps to avoid the large workload that is required for model redevelopment and can expand the functions of core models relatively quickly.

The Total Control of Water Supply and Water Consumption in Tianjin City Based on WAS Model

Water resources planning and management should constitute an integral part of the socio-economic development planning process. Models have become the core part of water resources management. In this paper, the Water Simulation and Allocation Model (WAS) was developed and applied in Tianjin City, China. The aim of the research is to provide the water control value based on pragmatic modeling approach to water planning and management in order to promote water allocation, recover ecosystem recovery. In 2030, in accordance with WAS model calculated, the ET goal control is the 643mm; the volume of sea water into the goal for 1.649 billion m3. Exploitation of deep underground water is about 3.06 billion m3. Domestic economy in rural areas are being met and the water control of domestic economy is about 37.87 billion m3; water for the Ecology is 9.51 billion m3.

Development of an irrigation scheduling software based on model predicted crop water stress

Modern irrigation scheduling methods are generally based on sensor-monitored soil moisture regimes rather than crop water stress. Crop water stress is difficult to measure in real-time, but can be computed using agricultural system models. In this study, an irrigation scheduling method and its facilitate software based on RZWQM2 model (Root Zone Water Quality Model) predicted crop water stress were developed and evaluated. The timing of irrigation was based on the occurrence of model-simulated water stress, while the depth of irrigation was based on the fraction of the soil moisture deficit (K) needed to replenish the soil water content (θ) at any given time to field capacity (θfc), i.e., from θt0 to θt0+K(θfc-θt0). The predicted water stress for different K values was tested based on RZWQM2 scenarios calibrated against data collected in a drip-irrigated corn (Zea mays L.) field near Greeley, Colorado, USA between 2008 and 2010, and in a sprinkler irrigated soybean [Glycine max (L.) Merr.] field in Noxubee, Mississippi, USA in 2014. For the Colorado site, the simulated full irrigation (K =1) using this newly developed water stress-based irrigation approach saved 30.5%, 17.3% and 7.1% in total irrigation depth in successive years, whereas higher frequency with 60–90% of full irrigation at each event (0.6 ≤ K ≤ 0.9) provided water savings of as much as 35%, 30%, and 16%, respectively. The water stress-based irrigation scheme showed that crop yield was not affected, with a negligible change about 0.03–3.81% decrease. These water savings were a result of the water stress-based irrigation regime maintaining sufficient water to meet crop root water uptake requirements without constantly fully rehydrating the soil, thereby minimizing evaporation from the soil surface and soil water storage after grain filling. For the Mississippi site, this newly developed water stress-based irrigation software could improve crop yield by 291 kg ha−1 though consume 3.43 cm more water than field irrigation regime. Similarly, high frequency irrigation (lower K) under water stress-based regime resulted in higher water use efficiency. This study suggested that the water stress-based irrigation scheme could save water use and maintain crop yield in semi-arid region, while in humid region it could increase crop yield while consume more water. Further work is needed to install this system in an irrigated field and test its performance under different climate and soil conditions.

An application of a water assessment and simulation model in the remediation of the eutrophication capacity of a tropical water system: Case study the Lake Obili in Yaounde (Cameroon)

Abstract Lake Obili is one of the most famous lakes in the city of Yaounde, Cameroon. Studies carried out in this lake showed that it was hyper eutrophic and therefore it represents a great danger because it is used for aquaculture, tourism and a suitable laboratory for hydro-biological engineering. It is thus very vital to restore this lake ecosystem that singles itself in the heart of the city of Yaounde. This can be greatly facilitated through the use of Water Quality Analysis Simulation Program (WASP) of the United State Environmental protection Agency (USEPA). The outcomes of the previous results obtained from EUTRO, a Subroutine of the WASP model specialised in determining eutrophication level have proven that the remediation of this lake can be achievable through the implementation of a wet dredging, the construction and restoration of a wastewater treatment plant, the implementation of environmental incentive policies and the arrangement of the access to the lake. The application of the model is a contribution to the scientific mastery of nutrient flow, lake functioning and possibilities of restauration of highly polluted tropical water bodies subjected to domestic and industrial pollution.

Can the agricultural AquaCrop model simulate water use and yield of a poplar short-rotation coppice?

We calibrated and evaluated the agricultural model AquaCrop for the simulation of water use and yield of a short‐rotation coppice (SRC) plantation with poplar (Populus) in East Flanders (Belgium) during the second and the third rotation (first 2 years only). Differences in crop development and growth during the course of the rotations were taken into account during the model calibration. Overall, the AquaCrop model showed good performance for the daily simulation of soil water content (R 2 of 0.57–0.85), of green canopy cover (R 2 > 0.87), of evapotranspiration (ET; R 2 > 0.76), and of potential yield. The simulated, total yearly water use of the SRC ranged between 55% and 85% of the water use of a reference grass ecosystem calculated under the same environmental conditions. Crop transpiration was between 67% and 93% of total ET, with lower percentages in the first than in the second year of each rotation. The observed (dry mass) yield ranged from 6.61 to 14.76 Mg ha−1 yr−1. A yield gap of around 30% was observed between the second and the third rotation, as well as between simulated and observed yield during the third rotation. This could possibly be explained by the expansion of the understory (weed) layer; the relative cover of understory weeds was 22% in the third year of the third rotation. The agricultural AquaCrop model simulated total water use and potential yield of the operational SRC in a reliable way. As the plantation was extensively managed, potential effects of irrigation and/or fertilization on ET and on yield were not considered in this study.

Modeling long-term water use of irrigated cropping rotations in the Texas High Plains using SWAT

The Ogalalla Aquifer is used to supplement insufficient precipitation for agricultural production in the semiarid Texas High Plains. However, decades of pumping combined with minimal recharge has resulted in decreased well capacity in most areas. A calibrated Soil and Water Assessment Tool (SWAT) model was used to compare simulated yields, crop water use, and required irrigation for crop rotations of the region using measured long-term (90 years) historical weather data. Crop rotations included continuous corn and cotton, corn–cotton, sorghum–cotton, cotton–winter wheat, and corn–winter wheat. Results demonstrated that a calibrated SWAT model simulated crop water use and yields well for all listed crops except cotton. The plant growth algorithms in SWAT appear unable to simulate representative cotton yields typical of cotton management in the Texas High Plains. A work-around for a limitation of the auto-irrigate function in SWAT to be suspended during the dormancy period of winter wheat was also used. Summary statistics for crop yield, crop water use, and irrigation were presented for all rotations. Long-term water use of simulations and irrigation probability exceedance statistics are presented for all simulated crops. These data may serve as a decision support tool for producers considering crop rotation strategies.

Parametric analysis of technology costs for CO2 storage in saline formations

Over the last decade, a substantial amount of economic, engineering, and geoscience research has focused on storing CO2 in geological formations. Of those different formations, storage in saline water-bearing formations represents the largest storage potential. Fossil fuel-based power plants in the U.S. (coal and natural gas) contributed to 40% of all CO2 emissions in 2008 and therefore represent an important factor to address atmospheric CO2 emissions.The Water, Energy and Carbon Sequestration Simulation Model (WECSsim) was developed to calculate water use and treatment options, CO2 injection volumes and the levelized cost of energy (LCOE) results for both a single representative power plant paired with a saline formation scenario, and a full power plant fleet. The details of the analysis presented here broadly demonstrate the sensitivity of CO2 capture and storage (CCS) costs in geologic saline formations with water extraction, treatment and reuse to changes in the water demands associated with implementing CCS across the power plant fleet (coal and natural gas).The majority of the coal and natural gas plants in the U.S. have an avoided cost of $70–200 per tonne of CO2. Storing 1.0Gt/yr of the nation’s 2.3Gt/yr total CO2 emissions returns an avoided (storage) cost of range 79–143 (57–81) $/t ($US 2013) under various scenarios. These scenarios include allowing competition between power plants for saline formation space to store CO2, varying the duration of the storage rights, and permitting the extraction of saline waters for treatment.Under the same 1Gt/yr captured scenario, the extracted and treated water volumes could offset 12% of the added water demand due to the parasitic energy requirements of CCS at the national level. The cost of water treatment, using a reverse osmosis system, ranges between approximately $3.20/m3 water (for larger, older coal-fired plants like the San Juan Power Generating Station) and $2.60/m3 water for natural gas combined cycle plants (such as the Oyster Creek Power Generating Station) with substantial variability in costs based on plant location and design. For context, the levelized cost of energy (LCOE) composition of the pulverized coal-based San Juan Generation Station is 52%, 43% and 5% for the base LCOE, parasitic energy requirements, and water extraction, treatment and utilization costs, respectively. Similarly, for the Oyster Creek natural gas combined cycle plant, these percentages are 64%, 33%, and 2% of the total LCOE, respectively. In both technology cases the parasitic energy requirement costs far outweigh the cost to extract, treat, transport, and utilize saline formation waters.Additional results indicate that of the 325 saline formations included in the national-level analysis, the Mt. Simon formation has an estimated capacity to hold 53% of all the CO2 generated from the U.S. coal and natural gas-based power plants without extracting and treating saline water. The St. Peter Sandstone formation could hold 43%, though with saline water extraction and treatment. These results suggest that focusing research, development and demonstration (RD&D) efforts on careful geologic site selection and reducing the parasitic energy penalty, and its respective costs, will help lower the overall cost of CCS across the U.S. coal and natural gas-based power plant fleet.