Non-drought Years Research Articles

AGRICULTURAL DROUGHT AND SOIL MOISTURE ANALYSIS USING SATELLITE IMAGE BASED INDICES

Abstract. The deficiency in rainfall leads to meteorological droughts. Its manifestations are visible both in the vegetation cover and soil moisture. The present study assessed the characteristics of agricultural drought following meteorological droughts. The study also assessed the severity of meteorological droughts and their manifestation on the agriculture and soil moisture in a semi-arid area. The study has been carried out for the Malaprabha sub-basin which partly covers three districts of North Interior Karnataka, India. India Meteorological Department’s (IMD) criteria have been used to identify the drought years, and its severity has been assessed through the Standard Precipitation Index (SPI). The IMD’s monthly rainfall data were used to identify the drought years and periods for the region. Among the drought years, the mild, moderate, and severe drought along with deficit and excess rainfall years were considered to assess and characterize the soil moisture conditions and the agricultural drought. The satellite image based indices for these selected years were constructed to determine the soil moisture conditions and the agricultural drought severity. The Temperature-Vegetation Dryness Index (TVDI) was used to determine the soil moisture conditions. The indices employed to determine the agriculture drought are NDVI, Thermal Condition Index (TCI), Vegetation Condition Index (VCI), and Vegetation Health Index (VHI). These satellite-based indices were calculated using the Landsat images of the selected drought and non-drought years. The results showed that the seasonal and annual drought are frequent in the study area. There are spatial and temporal variations in the drought years and their severity. The satellite-based indices clearly indicate the spatial variation in the agriculture droughts and its intensity. It has been found that the impact of drought on agriculture has significantly reduced due to the development of well-irrigation in the sub-basin. VHI is more appropriate in determining the agricultural drought and its characteristics.

Long‐term (37 years) impacts of low‐head dams on freshwater shrimp habitat connectivity in northeastern Puerto Rico

AbstractFreshwater migratory shrimp in Puerto Rico depend on watershed connectivity, from stream headwaters to the ocean, to complete their life cycle. Moreover, shrimp populations in different watersheds are known to be connected in an island‐wide metapopulation. However, low‐head dams paired with water intakes on streams draining the El Yunque National Forest (EYNF) reduce streamflow. Here, we examine the cumulative effects of low‐head dams on shrimp habitat connectivity over 37 years across seven EYNF watersheds. We calculate total and refugia habitat connectivity (where refugia habitat is defined as predator‐free upstream reaches above waterfalls >5 m in height) at a monthly time step using a habitat‐weighted index of longitudinal riverine connectivity, which incorporates location and operation of water intakes and streamflow variability. Findings indicate total and refugia habitat connectivity declined over 37 years (by 27% and 16%, respectively) as additional water intakes have been placed in lower reaches of watersheds. On a monthly time step, the proportion of streamflow withdrawn has the largest effect on habitat connectivity, with the result that connectivity is ~17% lower during drought years than in nondrought years and ~7% lower in dry compared with wet seasons. Our analysis of this long‐term dataset highlights how cumulative effects of low‐head dams paired with water intakes have reduced shrimp habitat connectivity. These results underscore the importance of reducing existing withdrawal rates in EYNF, and locating intakes where effects on connectivity are minimal, if conserving shrimp habitat is a management objective.

Sensitivity of grain yields to historical climate variability in India

Fluctuations in temperature and precipitation influence crop productivity across the planet. With episodes of extreme climate becoming increasingly frequent, buffering crop production against these stresses is a critical aspect of climate adaptation. In India, where grain production and diets are closely linked, national food supply is sensitive to the effect of climate variability on monsoon grain production. Here we quantitatively examine the historical (1966–2011) relationship between interannual variations in temperature and rainfall and rainfed yield variability for five monsoon crops—rice and four alternative grains (finger millet, maize, pearl millet, and sorghum). Compared to rice, we find that alternative grains are significantly less sensitive to climate variation and generally experience smaller declines in yield under climate extremes. However, maximizing harvested area allocations to coarse grains (i.e. holding maize production constant) reduced grain production by 12.0 Mtonnes (−17.2%) under drought conditions and 12.8 Mtonnes (−18.0%) during non-drought years (non-drought). Increasing the harvested area allocated to all alternative grains (i.e. including maize) can enhance production by +39.6% (drought) and by +37.0% (non-drought). These alternative grains therefore offer promise for reducing variations in Indian grain production in response to climate shocks, but avoiding grain production shortfalls from increased alternative grains will require yield improvements that do not compromise their superior climate resilience.

Comparison of climate–growth responses of montane and piedmont longleaf pine (Pinus palustris Mill.) chronologies in North Carolina

Montane longleaf pine tree-ring chronologies exhibit fidelity to summer soil-moisture conditions. Multi-century climate reconstructions using longleaf pine can provide insights into the natural range of moisture variability. Longleaf pine (Pinus palustris Mill.) ring width is associated with temperature and precipitation throughout its range, yet intrasite comparisons of climate and ring growth are limited and have not examined interior (i.e., montane vs. piedmont) populations. Here, we investigated remnant stands of montane and piedmont longleaf pine in central North Carolina and compared their sensitivity to summer climatic variables during 1935–2015. Summer precipitation and PDSI were better associated with tree-ring chronologies developed from latewood growth from both the montane (r = 0.429 PDSI, r = 0.563 precipitation) and piedmont (r = 0.252, r = 0.441) chronologies while correlations with temperature variables were either weak (r = − 0.249 maximum temperature montane, r = − 0.229 piedmont) or not significant. We examined longleaf pine latewood sensitivity to late-summer (July–September) climate conditions, drought detection, and differences in radial growth during drought and non-drought periods and found greater sensitivity of the montane chronology to these metrics. Specifically, the montane chronology was more sensitive to drought detection identifying all 11 droughts that occurred during the 81-year study period, while the piedmont chronology identified only 6 of the 11. Further, while significant differences in radial growth existed between drought and non-drought years for both chronologies, the montane chronology exhibited considerably greater growth range between these favorable and unfavorable periods. These results indicate the use of montane longleaf pine is preferable when reconstructing precipitation variability and when coupled with remnant stump data provide an opportunity to reconstruct summer climate variability.

Building A High-Resolution Vegetation Outlook Model to Monitor Agricultural Drought for the Upper Blue Nile Basin, Ethiopia

To reduce the impacts of drought, developing an integrated drought monitoring tool and early warning system is crucial and more effective than the crisis management approach that is commonly used in developing countries like Ethiopia. The overarching goal of this study was to develop a higher-spatial-resolution vegetation outlook (VegOut-UBN) model that integrates multiple satellite, climatic, and biophysical input variables for the Upper Blue Nile (UBN) basin. VegOut-UBN uses current and historical observations in predicting the vegetation condition at multiple leading time steps of 1, 3, 6, and 9 dekades. VegOut-UBN was developed to predict the vegetation condition during the main crop-growing season locally called “Kiremt” (June to September) using historical input data from 2001 to 2016. The rule-based regression tree approach was used to develop the relationship between the predictand and predictor variables. The results for the recent historic drought (2009 and 2015) and non-drought (2007) years are presented to evaluate the model accuracy during extreme weather conditions. The result, in general, shows that the predictive accuracy of the model decreases as the prediction interval increases for the cross-validation years. The coefficient of determination (R2) of the predictive and observed vegetation condition shows a higher value (R2 > 0.8) for one-month prediction and a relatively lower value (R2 ≅ 0.70) for three-month prediction. The result also reveals strong spatial integrity and similarity of the observed and predicted maps. VegOut-UBN was evaluated and compared with the Standardized Precipitation Index (SPI) (derived from independent rainfall datasets from meteorological stations) at different aggregate periods and with a food security status map. The result was encouraging and indicative of the potential application of VegOut-UBN for drought monitoring and prediction. The VegOut-UBN model could be informative in decision-making processes and could contribute to the development of operational drought monitoring and predictive models for the UBN basin.

Developing a satellite-based combined drought indicator to monitor agricultural drought: a case study for Ethiopia

Developing a robust drought monitoring tool is vital to mitigate the adverse impacts of drought. A drought monitoring system that integrates multiple agrometeorological variables into a single drought indicator is lacking in areas such as Ethiopia, which is extremely susceptible to this natural hazard. The overarching goal of this study is to develop a combined drought indicator (CDI-E) to monitor the spatial and temporal extents of historic agricultural drought events in Ethiopia. The CDI-E was developed by combining four satellite-based agrometeorological input parameters – the Standardized Precipitation Index (SPI), Land Surface Temperature (LST) anomaly, Standardized Normalized Difference Vegetation Index (stdNDVI) and Soil Moisture (SM) anomaly – for the period from 2001 to 2015. The method used to combine these indices is based on a quantitative approach that assigns a weight to each input parameter using Principal Component Analysis (PCA). The CDI-E results were evaluated using satellite-based gridded rainfall (3-month SPI) and crop yield data for 36 intra-country crop growing zones for a 15-year period (2001 to 2015). The evaluation was carried out for the main rainfall season, Kiremt (June-September), and the short rainfall season, Belg (February-May). The results showed that moderate to severe droughts were detected by the CDI-E across the food insecure regions reported by FEWS NET during Kiremt and Belg rainfall seasons. Relatively higher correlation coefficient values (r > 0.65) were obtained when CDI-E was compared with the 3-month SPI across the majority of Ethiopia. The spatial correlation analyses of CDI-E and cereal crop yields showed relatively good correlations (r > 0.5) in some of the crop growing zones in the northern, eastern and southwestern parts of the country. The CDI-E generally mapped the spatial and temporal patterns of historic drought and non-drought years and hence the CDI-E could potentially be used to develop an agricultural drought monitoring and early warning system in Ethiopia. Moreover, decision makers and donors may potentially use CDI-E to more accurately monitor crop yields across the food-insecure regions in Ethiopia.

Effects of A Severe Drought On Summer Abundance, Growth, and Movement of Cutthroat Trout In A Western Oregon Headwater Stream

Winter snowpack depth, snowmelt timing, and snowmelt duration are projected to change in the future, leading to increased frequency and severity of drought in the Pacific Northwest. In summer 2015, stream flows throughout the Pacific Northwest were at record low levels because of low winter snowpack conditions consistent with these climate projections. We explored effects of the 2015 low-snowpack-associated drought on Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) abundance, growth, and movement patterns in two 100m reaches ( 350 y old forests) of an unnamed perennial western Oregon headwater stream before (2 y) and during a severe drought. We found that the abundance of Cutthroat Trout declined substantially during the drought year, regardless of habitat availability, riparian forest age, or stream wood structure. Fish growth during summer was consistently negative during all 3 y of the study in both reaches. During the drought year, estimated abundance and total biomass of Cutthroat Trout declined in both reaches compared to the 2y prior. In all 3 y, the majority (76%) of fish in the reach with a young riparian forest stand moved >2 m from their release point. In contrast, across the 3 study years, only 26% of fish on average moved >2 m from their release point in the old-growth reach, which had more large wood and pool area. Across both reaches, in the non-drought years, most fish moved into pools (32.4%), but some moved to riffles (23.3%). During the drought year, of the fish that were recaptured, only upstream movement to pools were observed. There were no observed movements of recaptured fish to riffles. Overall, study results suggest that increasing severity of summer drought in the Pacific Northwest is likely to reduce the abundance of fish in small headwater streams, and the remaining fish preferentially use pool habitats such as those found in structurally complex streams.

Detecting drought impact on terrestrial biosphere carbon fluxes over contiguous US with satellite observations

With projections of increasing drought in the future, understanding how the natural carbon cycle responds to drought events is needed to predict the fate of the land carbon sink and future atmospheric CO2 concentrations and climate. We quantified the impacts of the 2011 and 2012 droughts on terrestrial ecosystem carbon uptake anomalies over the contiguous US (CONUS) relative to non-drought years during 2010–2015 using satellite observations and the carbon monitoring system—flux inversion modeling framework. Soil moisture and temperature anomalies are good predictors of gross primary production anomalies (R2 > 0.6) in summer but less so for net biosphere production (NBP) anomalies, reflecting different respiration responses. We showed that regional responses combine in complicated ways to produce the observed CONUS responses. Because of the compensating effect of the carbon flux anomalies between northern and southern CONUS in 2011 and between spring and summer in 2012, the annual NBP decreased by 0.10 ± 0.16 GtC in 2011, and increased by 0.10 ± 0.16 GtC in 2012 over CONUS, consistent with previous reported results. Over the 2011 and 2012 drought-impacted regions, the reductions in NBP were ∼40% of the regional annual fossil fuel emissions, underscoring the importance of quantifying natural carbon flux variability as part of an overall observing strategy. The NBP reductions over the 2011 and 2012 CONUS drought-impacted region were opposite to the global atmospheric CO2 growth rate anomaly, implying that global atmospheric CO2 growth rate is an offsetting effect between enhanced uptake and emission, and enhancing the understanding of regional carbon-cycle climate relationship is necessary to improve the projections of future climate.

Investigation and simulations of changes in the relationship of precipitation-runoff in drought years

The frequency and intensity of drought could be increasing with global warming. When drought occurs, the runoff generation process and the precipitation-runoff relationship might change. In this study, the precipitation-runoff relationship in drought years was systematically investigated in the largest freshwater lake basin of China, namely, the Poyang Lake Basin. The results showed that the precipitation-runoff relationship changed significantly (p < 0.05) in drought years. The annual runoff coefficient in drought years decreased by 24.1% compared with that in non-drought years. The decreased magnitude of runoff coefficient had a significant positive relationship (p < 0.01) with the drought severity, i.e., the standardized precipitation index of the year. Two hydrological models calibrated by the objective function Nash-Sutcliffe efficiency significantly overestimated runoff in drought years. Three additional objective functions that are sensitive to low flow simulations significantly improved the accuracy of runoff simulation in drought years. Therefore, we recommend that the selected objective functions for runoff simulation in drought years should be sensitive to low flow simulations. Otherwise, the water resources availability will be overestimated in drought years.

Impact of extreme drought and incentive programs on flooded agriculture and wetlands in California's Central Valley.

BackgroundBetween 2013 and 2015, a large part of the western United States, including the Central Valley of California, sustained an extreme drought. The Central Valley is recognized as a region of hemispheric importance for waterbirds, which use flooded agriculture and wetlands as habitat. Thus, the impact of drought on the distribution of surface water needed to be assessed to understand the effects on waterbird habitat availability.MethodsWe used remote sensing data to quantify the impact of the recent extreme drought on the timing and extent of waterbird habitat during the non-breeding season (July–May) by examining open water in agriculture (rice, corn, and other crops) and managed wetlands across the Central Valley. We assessed the influence of habitat incentive programs, particularly The Nature Conservancy’s BirdReturns and The Natural Resources Conservation Service’s Waterbird Habitat Enhancement Program (WHEP), at offsetting habitat loss related to drought.ResultsOverall, we found statistically significant declines in open water in post-harvest agriculture (45–80% declines) and in managed wetlands (39–60% declines) during the 2013–2015 drought compared to non-drought years during the period of 2000–2011. Crops associated with the San Joaquin Basin, specifically corn, as well as wetlands in that part of the Central Valley exhibited larger reductions in open water than rice and wetlands in the Sacramento Valley. Semi-permanent wetlands on protected lands had significantly lower (39–49%) open water in the drought years than those on non-protected lands while seasonal wetlands on protected lands had higher amounts of open water. A large fraction of the daily open water in rice during certain times of the year, particularly in the fall for BirdReturns (61%) and the winter for WHEP (100%), may have been provided through incentive programs which underscores the contribution of these programs. However, further assessment is needed to know how much the incentive programs directly offset the impact of drought in post-harvest rice by influencing water management or simply supplemented funding for activities that might have been done regardless.DiscussionOur landscape analysis documents the significant impacts of the recent extreme drought on freshwater wetland habitats in the Central Valley, the benefits of incentive programs, and the value of using satellite data to track surface water and waterbird habitats. More research is needed to understand subsequent impacts on the freshwater dependent species that rely on these systems and how incentive programs can most strategically support vulnerable species during future extreme drought.

Use of airborne PM10 concentrations at air quality monitoring sites in Imperial County, California, as an indication of geographical influences on lung health during drought periods: a time-series analysis

Background2012–16 marked the worst drought in California, USA, in more than a century. Droughts are expected to recur in broader areas as a result of anthropogenic climate change. The Salton Sea, a landlocked depression without natural river inflow, is almost entirely dependent on agricultural irrigation of Imperial Valley's 475 000 acres of farmland, although its water level has been diminishing because of decreased precipitation and river flow. Exposure of the lakebed and ground heating in an already arid climate might cause an increase in airborne PM10 (particulate matter less than 10 μm in diameter), reactive nitrogen, and ground-level ozone, exacerbating asthma symptoms. During the most severe drought years, admissions of children to the emergency department for asthma-related symptoms in Imperial County were among the highest in California and double the number for the entire state. However, previous analyses have not taken into account environmental mediators with more specific geographical granularity than the county level. MethodsIn this analysis, we used 2006–16 data from the US Drought Monitor and the five air quality monitoring stations (AQMS) within Imperial County, CA, USA. To reconcile sampling differences between 7-day drought severity reports and 6-day PM10 measurements, a date windowing function was applied to match each PM10 measurement to the drought severity value at the most closely related point in absolute time. Upon visually examining the data, lower concentrations of PM10 appeared to drive the correlation between AQMS. Therefore, in two time series—all years and non-drought years only—all concentrations of PM10 that were lower than 75 ppm were removed, and the remaining concentrations were used to measure correlations between AQMS. FindingsPM10 concentrations across all years were poorly correlated between AQMS (r=0·41–0·80; p<0·05). When removing PM10 concentrations lower than 75 ppm and examining only the remaining values, the correlation coefficients for these values decreased (r=0·16–0·53; p<0·05). When removing drought years (2012 onwards), these values were slightly more correlated in comparisons between some AQMS than across all observed years (r=0·46–0·77; p<0·05). InterpretationThe inconsistency in PM10 concentrations between AQMS on high PM10 days and during drought years suggests that different AQMS do not experience the same changes in air quality, particularly on days most likely to cause asthma exacerbations. This finding indicates a geographical component of air-quality differences and the potential for children near rural farmland to be more susceptible to asthma and lung disease. Future research regarding respiratory health in drought areas will provide a perspective on under-represented local and regional environmental challenges. Drought is one of the most expensive natural events from a number of economic and public health stances, and findings in support of the health implications of agriculture and water use have broader potential implications for water policy, drought mitigation strategies, and health improvement. FundingNone.

Effects of Annual Droughts on Fish Communities in Mississippi Sound Estuaries

The Mississippi coastal region has two major rivers and four smaller rivers influencing the estuaries that make up the Mississippi Sound. The islands off Mississippi create a barrier which allows the area to be a widespread, productive estuarine region. With such a dependence on discharge from the drainages, it is important to understand the effect of salinity regimes on fish communities. Drought conditions in other regions have been shown to dramatically change the fish community structure. We used the long running Interjurisdictional Fisheries Program database (2006–2014) within Mississippi state waters and compared yearly fish communities between drought and non-drought years. Non-metric Multidimensional Scaling (nMDS), Analysis of Similarity (ANOSIM), and Indicator Species Analysis (ISA) were used to compare drought and non-drought conditions in the Mississippi Sound. During 2006 and 2007, which were identified as drought years by the Palmer Drought Severity Index (PDSI), differences in fish community structure were identified and compared to non-drought years (2008–2009 and 2011–2014). The ISA identified a total of eight species that were significantly influenced by drought years. Of the eight species, the abundance of seven species significantly decreased while the abundance of one species significantly increased. With an increasing human population in central and south Mississippi, pressure on freshwater resources is likely to increase, resulting in possible changes in the fish community dynamics of the Mississippi Sound. Understanding the influence of decreased river discharges will assist managers in determining the impacts of freshwater withdrawals during base flow periods.

Extreme drought alters frequency and reproductive success of floaters in Willow Flycatchers

ABSTRACT Changes in habitat quality, including those caused by extreme events like droughts and floods, could alter costs and benefits of territoriality and thereby the prevalence and reproductive consequences for individuals capable of breeding that do not do so (floaters). We studied floating behavior in a population of Southwestern Willow Flycatchers (Empidonax traillii extimus) in central Arizona during one year of extreme drought, one year of lake inundation, and three years of near average precipitation. In all years, most floaters were second year (SY) males, and most subsequently settled outside of the patch where they were detected in the floating year, suggesting that floaters did not “queue” at high-quality territories in order to achieve higher reproductive success in subsequent years. Instead, cohorts that floated in non-drought years had lower apparent survival and lower reproductive success compared to territorial birds. In the extreme drought year, however, the number of floaters was 1.5 t...

Simulating system‐wide effects of reducing irrigation withdrawals in a disputed river basin

AbstractStakeholders in river systems often target larger upstream water consumers as an intuitive solution for increasing flows for downstream ecological needs. Within regulated river systems, simplistic panaceas may have unexpected and unintended results at a watershed level. The Apalachicola–Chattahoochee–Flint River Basin is a large watershed in the south‐eastern United States whose management has been the source of conflict for several decades. This paper tests the hypothesis of whether a reduction in consumptive losses to Flint River flows through the large‐scale implementation of water‐saving agricultural irrigation technologies and practices will have a positive effect on downstream ecosystem water requirements in the Apalachicola River. An existing integrated reservoir/reach model was used to explore multiple irrigation water use scenarios.Because of current federal reservoir operating rules in the Chattahoochee River, irrigation decreases in the Flint River do not always directly translate to elevated flows downstream in the Apalachicola River. In drought years, a large percentage of the Flint River water savings is captured as greater storage volume at upstream Chattahoochee reservoirs because of a requirement to supplement downstream flows to a prescribed minimum level. In nondrought years, the majority of irrigation decreases translate to increased flow in the Apalachicola River. Given these simulation results, public policy decisions need to be formulated with regard to what portion of the Flint River water savings from changing irrigation practices in drought years should be allocated to the upstream Chattahoochee storage reservoirs and what portion to supporting downstream environmental and social needs in the Apalachicola watershed.

Heightened fire probability in Indonesia in non-drought conditions: the effect of increasing temperatures

In Indonesia, drought driven fires occur typically during the warm phase of the El Niño Southern Oscillation. This was the case of the events of 1997 and 2015 that resulted in months-long hazardous atmospheric pollution levels in Equatorial Asia and record greenhouse gas emissions.Nonetheless, anomalously active fire seasons have also been observed in non-drought years. In this work, we investigated the impact of temperature on fires and found that when the July-October (JASO) period is anomalously dry, the sensitivity of fires to temperature is modest. In contrast, under normal-to-wet conditions, fire probability increases sharply when JASO is anomalously warm. This describes a regime in which an active fire season is not limited to drought years. Greater susceptibility to fires in response to a warmer environment finds support in the high evapotranspiration rates observed in normal-to-wet and warm conditions in Indonesia. We also find that fire probability in wet JASOs would be considerably less sensitive to temperature were not for the added effect of recent positive trends. Near-term regional climate projections reveal that, despite negligible changes in precipitation, a continuing warming trend will heighten fire probability over the next few decades especially in non-drought years. Mild fire seasons currently observed in association with wet conditions and cool temperatures will become rare events in Indonesia.

Holy Cows or Cash Cows? The Economic Return to Livestock in Rural India

AbstractThis paper revisits recent claims that poor households owning cattle in developing countries settings do not behave according to the tenets of capitalism. We point out that the discussion was based on evidence from one single year only, while cows and buffalos are assets whose return varies through time. In drought years, when fodder is scarce and more expensive, milk production is lower and profits are low. In nondrought years, when fodder is abundant and cheaper, milk production is higher and profits can be considerably higher. Therefore, the return on cows and buffalos, like that of many stocks traded on Wall Street, is positive in some years and negative in others. The fact that in a given year the observed return on a risky asset is negative could certainly not be used as a contradiction of one of the basic tenets of capitalism. We report evidence from 3 years of data on the return on cows and buffalos in the district of Anantapur and show that in one of the 3 years returns are very high, whi...

The Texas Quail Index: Evaluating Predictors of Northern Bobwhite Productivity and Abundance Using Citizen Science

Annual abundance of northern bobwhites (Colinus virginianus) fluctuates drastically in semi-arid environments (e.g., Texas), which complicates the ability of wildlife biologists and quail managers to predict annual bobwhite productivity and relative abundance for the ensuing hunting season. The Texas Quail Index (TQI) was a 5-year citizen science project that evaluated several indices as predictors of bobwhite productivity and abundance during the subsequent fall. Indices included spring cock-call counts, forb species richness, simulated-nest fate, potential nest-site density, scent station visitation rates, roadside counts, fall covey call counts, and harvest data. Spring cock-call counts explained only 41% of the variation in fall bobwhite abundance across all study sites in years 1–4; yet explained 89% of the variation in year 5. The percentage of juveniles in the fall population (an index of bobwhite productivity) was significantly lower in year 5. All study sites experienced drought conditions throughout year 5 based on the Palmer Drought Severity Index (PDSI). Thus, drought conditions in semi-arid environments result in reduced productivity compared to non-drought years. Our results suggest low recruitment during drought years makes fall bobwhite abundance more predictable than during non-drought years. Wildlife biologists and quail managers should have a better ability to predict bobwhite productivity and fall abundance in drought years by recording spring cock-call counts.

Responses of Critically Endangered migratory Swift Parrots to variable winter drought

Migratory birds spend a large proportion of their lives within non-breeding habitats. However, knowledge of how they respond to variable winter resources is limited, especially for small migratory species. Citizen science programs provide an effective way to collect data on small migrants over large spatio-temporal scales. Here we present survey data for the Critically Endangered Swift Parrot (Lathamus discolor) that were collected by hundreds of volunteers over 7 years across the species' winter range. Swift Parrots were detected in 23% of the 4035 surveys. Linear mixed models were used to examine variation in Swift Parrot abundance and correlations with climate variables. During non-drought years Swift Parrots concentrated within Victorian habitats. However, when Victoria was in drought, the response of the birds depended on the extent of drought conditions throughout the winter range. Consecutive years of drought in Victoria resulted in the population migrating over 1000 km further to drought refuge habitat in New South Wales. This study provides a rare demonstration of the large spatio-temporal responses of a migratory bird population to extreme climate conditions across its winter range. It demonstrates both variable and repeated use of winter habitats, and highlights the need for conservation management at large spatio-temporal scales.

A comprehensively quantitative method of evaluating the impact of drought on crop yield using daily multi-scale SPEI and crop growth process model.

The quantitative evaluation of the impact of drought on crop yield is one of the most important aspects in agricultural water resource management. To assess the impact of drought on wheat yield, the Environmental Policy Integrated Climate (EPIC) crop growth model and daily Standardized Precipitation Evapotranspiration Index (SPEI), which is based on daily meteorological data, are adopted in the Huang Huai Hai Plain. The winter wheat crop yields are estimated at 28 stations, after calibrating the cultivar coefficients based on the experimental site data, and SPEI data was taken 11 times across the growth season from 1981 to 2010. The relationship between estimated yield and multi-scale SPEI were analyzed. The optimum time scale SPEI to monitor drought during the crop growth period was determined. The reference yield was determined by averaging the yields from numerous non-drought years. From this data, we propose a comprehensive quantitative method which can be used to predict the impact of drought on wheat yields by combining the daily multi-scale SPEI and crop growth process model. This method was tested in the Huang Huai Hai Plain. The results suggested that estimation of calibrated EPIC was a good predictor of crop yield in the Huang Huai Hai Plain, with lower RMSE (15.4%) between estimated yield and observed yield at six agrometeorological stations. The soil moisture at planting time was affected by the precipitation and evapotranspiration during the previous 90days (about 3months) in the Huang Huai Hai Plain. SPEIG90 was adopted as the optimum time scale SPEI to identify the drought and non-drought years, and identified a drought year in 2000. The water deficit in the year 2000 was significant, and the rate of crop yield reduction did not completely correspond with the volume of water deficit. Our proposed comprehensive method which quantitatively evaluates the impact of drought on crop yield is reliable. The results of this study further our understanding why the adoption of counter measures against drought is important and direct farmers to choose drought-resistant crops.

Development of probabilistic operating rules for Hluhluwe Dam, South Africa

Hluhluwe Dam, with a 30 million m3 reservoir that supplies water for irrigation and Hluhluwe municipality in Kwa-Zulu Natal Province, South Africa, was consistently experiencing low storage levels over several non-drought years since 2001. The dam was operated by rules of thumb and there were no records of water releases for irrigation - the main user of the dam. This paper describes an assessment of the historic behaviour of the reservoir since its completion in 1964 and the development of operating rules that accounted for: i) the multiple and different levels of reliability at which municipal and irrigation demands need to be supplied, and ii) inter-annual and inter-decadal variability of climate and inflows into the dam. The assessment of the behaviour of the reservoir was done by simulation assuming trigonometric rule curves that were optimized to maximize both yield and storage state using the SCE-UA method. The resulting reservoir behaviour matched the observed historic trajectory reasonably well and indicated that the dam has mainly been operated at a demand of 10 million m3/year until 2000 when the demand suddenly rose to 25 million m3/year. Operating rules were developed from a statistical analysis of the base yields from 500 simulations of the reservoir each using 5 year-long stochastically generated sequences of inflows, rainfall and evaporation. After the implementation of the operating rules in 2009, the storage state of the dam improved and matched those of other reservoirs in the region that had established operating rules.