Where should livestock graze? Integrated modeling and optimization to guide grazing management in the Cañete basin, Peru

Integrated watershed management allows decision-makers to balance competing objectives, for example agricultural production and protection of water resources. Here, we developed a spatially-explicit approach to support such management in the Cañete watershed, Peru. We modeled the effect of grazing management on three services – livestock production, erosion control, and baseflow provision – and used an optimization routine to simulate landscapes providing the highest level of services. Over the entire watershed, there was a trade-off between livestock productivity and hydrologic services and we identified locations that minimized this trade-off for a given set of preferences. Given the knowledge gaps in ecohydrology and practical constraints not represented in the optimizer, we assessed the robustness of spatial recommendations, i.e. revealing areas most often selected by the optimizer. We conclude with a discussion of the practical decisions involved in using optimization frameworks to inform watershed management programs, and the research needs to better inform the design of such programs

Rice Intensification in a Changing Environment: Impact on Water Availability in Inland Valley Landscapes in Benin

This study assesses the impact of climate change on hydrological processes under rice intensification in three headwater inland valley watersheds characterized by different land conditions. The Soil and Water Assessment Tool was used to simulate the combined impacts of two land use scenarios defined as converting 25% and 75% of lowland savannah into rice cultivation, and two climate scenarios (A1B and B1) of the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios. The simulations were performed based on the traditional and the rainfed-bunded rice cultivation systems and analyzed up to the year 2049 with a special focus on the period of 2030–2049. Compared to land use, climate change impact on hydrological processes was overwhelming at all watersheds. The watersheds with a high portion of cultivated areas are more sensitive to changes in climate resulting in a decrease of water yield of up to 50% (145 mm). Bunded fields cause a rise in surface runoff projected to be up to 28% (18 mm) in their lowlands, while processes were insignificantly affected at the vegetation dominated-watershed. Analyzing three watersheds instead of one as is usually done provides further insight into the natural variability and therefore gives more evidence of possible future processes and management strategie

Influence of Bioenergy Crop Production and Climate Change on Ecosystem Services

Land use change can significantly affect the provision of ecosystem services and the effects could be exacerbated by projected climate change. We quantify ecosystem services of bioenergy‐based land use change and estimate the potential changes of ecosystem services due to climate change projections. We considered 17 bioenergy‐based scenarios with Miscanthus, switchgrass, and corn stover as candidate bioenergy feedstock. Soil and Water Assessment Tool simulations of biomass/grain yield, hydrology, and water quality were used to quantify ecosystem services freshwater provision (FWPI), food (FPI) and fuel provision, erosion regulation (ERI), and flood regulation (FRI). Nine climate projections from Coupled Model Intercomparison Project phase‐3 were used to quantify the potential climate change variability. Overall, ecosystem services of heavily row cropped Wildcat Creek watershed were lower than St. Joseph River watershed which had more forested and perennial pasture lands. The provision of ecosystem services for both study watersheds were improved with bioenergy production scenarios. Miscanthus in marginal lands of Wildcat Creek (9% of total area) increased FWPI by 27% and ERI by 14% and decreased FPI by 12% from the baseline. For St. Joseph watershed, Miscanthus in marginal lands (18% of total area) improved FWPI by 87% and ERI by 23% while decreasing FPI by 46%. The relative impacts of land use change were considerably larger than climate change impacts in this paper. Editor’s note: This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140015/1/jawr12591_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/140015/2/jawr12591.pd

Hydrologic and water quality impacts from perennial crop production on marginal lands

Marginal lands are proposed as a viable option for producing biofeedstocks as these lands are not heavily engaged in agricultural production or may not be suitable for intensive row-crop food/feed production. However, meeting biofeedstock production goals will require large amount of marginal lands and the unintended consequences of producing biofeedstocks on marginal lands are not fully clear. The overall goal of this study was to evaluate the productivity of biofeedstocks on marginal lands and the potential impacts on hydrologic and water quality processes from the land use conversion. This study was conducted in the Upper Mississippi River Basin (UMRB). First, the suitability of marginal lands in this region was evaluated for the growth of three candidate biofeedstock crops, switchgrass, Miscanthus and hybrid poplar. The evaluation was conducted using a fuzzy logic based land suitability evaluation method. Then, the simulation of switchgrass and Miscanthus growth during their establishment periods in the Soil and Water Assessment Tool (SWAT) model was improved. Finally, the model was used to evaluate the impacts on hydrologic and water quality processes due to production of switchgrass and Miscanthus on marginal lands in the UMRB region. The results indicated that 23% of the UMRB area included marginal lands. Among these lands, 40% of them were poorly suitable for the production of biofeedstock crops. Biofeedstocks produced from these marginal lands could be converted to biofuels that contributed 14 to 25% of the 132 billion liter biofuel goals set by the Energy Independence and Security Act (EISA) 2007. The model simulation results indicated that producing perennial biofeedstock crops on marginal land would reduce annual stream flow by 20% and 29% and sediment load by 26% to 35% at the watershed outlet. The reduction was less during the establishment periods of perennial grasses (first 2 to 3 years of switchgrass and 2 to 4 years of Miscanthus) than during the post establishment periods. The results of this study indicated that marginal land in the UMRB region could be a viable choice of land resources for biofuel development and could be used to produce almost one quarter of biofuel production goals. At the same time, water quality in the watershed could be improved. The information could be used by stakeholders to create regional biofuel development and watershed management plans

Effect of bioenergy crops and fast growing trees on hydrology and water quality in the Little Vermilion River Watershed

Energy security and sustainability require a suite of biomass crops, including woody species. Short rotation woody crops (SRWCs) such as Populus have great potential as biofuel feedstocks. Quantifying biomass yields of bioenergy crop and hydrologic and water quality responses to growth is important should it be widely planted in the Midwestern U.S. Subsurface tile drainage systems enable the Midwest area to become highly productive agricultural lands, but also create environmental problems like nitrate-N contamination of the water it drains. The Soil and Water Assessment Tool (SWAT) has been used to model watersheds with tile drainage, but the new tile drainage routine in SWAT2012 has not been fully tested. The objectives of this study were to develop algorithms and growth parameters of Populus in Agricultural Land Management Alternative with Numerical Assessment Criteria (ALMANAC) and SWAT models, compare performance of tile drainage routines in SWAT2009 and SWAT2012 in simulating tile drainage, and simulate biomass yields of bioenergy crops and the impacts of their impacts on water quantity and quality for a typical tile-drained watershed in the Midwest USA. The functional components and parameters of hybrid poplar Tristis #1 (Populus balsamifera L. × P.tristis Fisch) and eastern cottonwood (Populus deltoides Bartr.) were determined, and related algorithms improved in ALMANAC and SWAT based on improved simulation of leaf area, plant biomass and biomass partitioning. Long-term (1991-2003) field site and river station data from the Little Vermilion River (LVR) watershed in Illinois were used to evaluate performance of tile drainage routines in SWAT2009 revision 528 (the old routine) and SWAT2012 revision 615 and 645 (the new routine). Calibrated monthly tile flow, surface flow, nitrate in tile and surface flow, sediment and annual corn and soybean yield results at field sites, and flow, sediment load and nitrate load at the river station for the old and new tile drainage routines were compared with observed values. Crop residue from corn stover, perennial grasses, switchgrass and Miscanthus, and hybrid poplar trees were considered as potential bioenergy crops for the LVR watershed. SWAT2012 (Revision 615) with the new tile drainage routine (DRAINMOD routine) and improved perennial grass and tree growth simulation was used to model long-term annual biomass yields, flow, tile flow, sediment load, total nitrogen, nitrate load in flow, nitrate in tile flow, soluble nitrogen, organic nitrogen, total phosphorus, mineral phosphorus and organic phosphorus under various bioenergy scenarios in the LVR watershed. Simulated results from different bioenergy crop scenarios were compared with those from the baseline. Tree growth calibration and validation results showed that improved algorithms of leaf area index (LAI) and biomass simulation and suggested values and potential parameter range for hybrid poplar Tristis #1 and Eastern cottonwood ( Populus deltoides Bartr.) were reasonable, and performance of the modified ALMANAC in simulating LAI, aboveground biomass and root biomass of Populus was good. Performance of the modified SWAT simulated hybrid poplar LAI and aboveground woody biomass (PBIAS: -57 ~ 7%, NSE: 0.94 ~ 0.99, and R2: 0.74 ~ 0.99), and cottonwood aboveground biomass, seasonal mean runoff, mean sediment, mean nitrate-N and total nitrate-N were satisfactory (PBIAS: -39 ~ 11%, NSE: 0.86 ~ 0.99, and R2: 0.93 ~ 0.99). Additionally, tile drainage calibration and validation results indicated that the new routine provides acceptable simulated tile flow (NSE = 0.50 ~ 0.68), and nitrate in tile flow (NSE = 0.50 ~ 0.77) for field sites, while the old routine simulated tile flow (NSE = -0.77~ -0.20) and nitrate in tile flow (NSE = -0.99 ~ 0.21) for the field site with constant tile spacing were unacceptable. The new modified curve number calculation method in revision 645 (NSE = 0.56 ~ 0.82) better simulated surface runoff than revision 615 (NSE = -5.95 ~ 0.5). Bioenergy crop simulation results showed that 38% corn stover removal (66,439 Mg/yr) with combination of Miscanthus both on highly erodible areas and marginal land (19,039 Mg/yr) provided the highest biofeedstock production. Flow, tile flow, erosion and nutrient losses were slightly reduced under bioenergy crop scenarios of Miscanthus, switchgrass, and hybrid poplar on highly erodible areas, marginal land and marginal land with forest. The increase in sediment load and nutrient losses resulting from corn stover removal could be offset under scenarios with various combinations of bioenergy crops. Corn stover removal with bioenergy crops both on highly erodible areas and marginal land could provide more biofuel production relative to the baseline, and was beneficial to hydrology and water quality at the watershed scale. The modified ALMANAC and SWAT can be used for biofeedstock production modeling for Populus. The modified SWAT model can be used for Populus biofeedstock production modeling and hydrologic and water quality response to its growth. The improved algorithms of LAI and biomass simulation for tree growth should also be useful for other process based models, such as SWAT, EPIC and APEX. Tile drainage calibration and validation results provided reasonable parameter sets for the old and new tile drainage routines to accurately simulate hydrologic processes in mildly-sloped watersheds. Bioenergy crop simulation results provided guidance for further research on evaluation of bioenergy crop scenarios in a typical extensively tile-drained watershed in the Midwestern US

Economic and hydrologic impacts

Presented at Meeting irrigation demands in a water-challenged environment: SCADA and technology: tools to improve production: a USCID water management conference held on September 28 - October 1, 2010 in Fort Collins, Colorado.Includes bibliographical references.Reduced surface water supplies in the Southern San Joaquin Valley of California in recent years have forced growers to make difficult decisions regarding cropping, irrigation practices, and groundwater use. There is interest in objectively quantifying economic and hydrologic impacts of these reductions at levels ranging from locally-affected communities to the State and Federal governments. However, the ability to analyze impacts is limited by the unavailability of timely disaggregated data. This paper explores the opportunity to apply satellite remote sensing of crop evapotranspiration and biomass production to increase information available and perform objective analysis of the actual economic and hydrologic impacts incurred

Potential impacts on ecosystem services of land use transitions to second-generation bioenergy crops in GB

We present the first assessment of the impact of land use change (LUC) to second-generation (2G) bioenergy crops on ecosystem services (ES) resolved spatially for Great Britain (GB). A systematic approach was used to assess available evidence on the impacts of LUC from arable, semi-improved grassland or woodland/forest, to 2G bioenergy crops, for which a quantitative ‘threat matrix’ was developed. The threat matrix was used to estimate potential impacts of transitions to either Miscanthus, short-rotation coppice (SRC, willow and poplar) or short-rotation forestry (SRF). The ES effects were found to be largely dependent on previous land uses rather than the choice of 2G crop when assessing the technical potential of available biomass with a transition from arable crops resulting in the most positive effect on ES. Combining these data with constraint masks and available land for SRC and Miscanthus (SRF omitted from this stage due to lack of data), south-west and north-west England were identified as areas where Miscanthus and SRC could be grown, respectively, with favourable combinations of economic viability, carbon sequestration, high yield and positive ES benefits. This study also suggests that not all prospective planting of Miscanthus and SRC can be allocated to agricultural land class (ALC) ALC 3 and ALC 4 and suitable areas of ALC 5 are only minimally available. Beneficial impacts were found on 146 583 and 71 890 ha when planting Miscanthus or SRC, respectively, under baseline planting conditions rising to 293 247 and 91 318 ha, respectively, under 2020 planting scenarios. The results provide an insight into the interplay between land availability, original land uses, bioenergy crop type and yield in determining overall positive or negative impacts of bioenergy cropping on ecosystems services and go some way towards developing a framework for quantifying wider ES impacts of this important LUC

Carbon, land and water: a global analysis of the hydrologic dimensions of climate change mitigation through afforestation / reforestation

Climate change / Water supply / Forests / Land use / Afforestation / Reforestation / Water balance / Models / Evapotranspiration / Precipitation / Water use / Ecosystems

A Watershed Scale Evaluation of Selected Second Generation Biofeedstocks on Water Quality

This study compares a novel simulation approach to the conventional Soil and Water Assessment Tool (SWAT) modeler\u27s approach for targeting biofuel crop production on marginal lands. In conventional SWAT modeling approach, non-spatial definition of hydrological response units (HRUs) results in the simulation of biofuel crops on both marginal and non-marginal land. This study provides an alternative approach in which a marginal-land raster was integrated into the land use and land cover (LULC) raster in such a way that the land uses were divided into marginal and non-marginal components. This modified LULC was used for model setup which resulted in marginal and non-marginal HRUs. This approach was evaluated for the L\u27Anguille River watershed (LRW) by calibrating and validating for total flow, surface flow, base flow, sediment, total phosphorus, and nitrate-nitrogen followed by the simulation of biofuel crops only on marginal HRUs. The results were analyzed for two cellulosic (second generation) biofuel crops: switchgrass (Panicum virgatum L.) and miscanthus (Miscanthus x giganteus). Compared to novel modeling approach, simulations using the conventional approach showed an increase in sediments by 20% and 61%, total phosphorus by 17% and 53%, and total nitrogen by 25% and 65% for the switchgrass and miscanthus, respectively. Compared to simulated pollutant losses from a mix of baseline row crops, switchgrass and miscanthus showed 94% and 78% decrease in sediment, 96% and 90% decrease in total phosphorus, and 80% and 67% decrease in total nitrogen, respectively. This study provided a novel approach to incorporate marginal land into the SWAT model and the model outputs suggest that producing perennial grass biofuel crops on marginal lands of the LRW resulted in lower sediment, total phosphorus, and total nitrogen losses than that obtained by conventional SWAT modeling. Pollutant losses from the non-targeted marginal HRUs explained the differences in the sediment, total phosphorus, and total nitrogen losses. The simulation results also suggested that substantial reduction in pollutant losses could be achieved by replacing baseline row crops with perennial grass crops on marginal lands in the LRW

Benefits of greenhouse gas mitigation on the supply, management, and use of water resources in the United States

Climate change impacts on water resources in the United States are likely to be far-reaching and substantial because the water is integral to climate, and the water sector spans many parts of the economy. This paper estimates impacts and damages from five water resource-related models addressing runoff, drought risk, economics of water supply/demand, water stress, and flooding damages. The models differ in the water system assessed, spatial scale, and unit of assessment, but together provide a quantitative and descriptive richness in characterizing water sector effects that no single model can capture. The results, driven by a consistent set of greenhouse gas (GHG) emission and climate scenarios, examine uncertainty from emissions, climate sensitivity, and climate model selection. While calculating the net impact of climate change on the water sector as a whole may be impractical, broad conclusions can be drawn regarding patterns of change and benefits of GHG mitigation. Four key findings emerge: 1) GHG mitigation substantially reduces hydro-climatic impacts on the water sector; 2) GHG mitigation provides substantial national economic benefits in water resources related sectors; 3) the models show a strong signal of wetting for the Eastern US and a strong signal of drying in the Southwest; and 4) unmanaged hydrologic systems impacts show strong correlation with the change in magnitude and direction of precipitation and temperature from climate models, but managed water resource systems and regional economic systems show lower correlation with changes in climate variables due to non-linearities created by water infrastructure and the socio-economic changes in non-climate driven water demand