We are evaluating dryland cotton production in Martin County, Texas, measuring cotton lint yield per unit of rainfall. Our goal is to collect rainfall data per 250 - 400 ha. Upon selection of a rainfall gauge, we realized that the cost of using, for example, a tipping bucket-type rain gauge would be too expensive and thus searched for an alternative method. We selected an all-in-one commercially available weather station; hereafter, referred to as a Personal Weather Station (PWS) that is both wireless and solar powered. Our objective was to evaluate average measurements of rainfall obtained with the PWS and to compare these to measurements obtained with an automatic weather station (AWS). For this purpose, we installed four PWS deployed within 20 m of the Plant Stress and Water Conservation Meteorological Tower that was used as our AWS, located at USDA-ARS Cropping Systems Research Laboratory, Lubbock, TX. In addition, we measured and compared hourly average values of short-wave irradiance (Rg), air temperature (Tair) and relative humidity (RH), and wind speed (WS), and calculated values of dewpoint temperature (Tdew). This comparison was done over a 242-day period (1 October 2022-31 May 2023) and results indicated that there was no statistical difference in measurements of rainfall between the PWS and AWS. Hourly average values of Rg measured with the PWS and AWS agreed on clear days, but PWS measurements were higher on cloudy days. There was no statistical difference between PWS and AWS hourly average measurements of Tair, RH, and calculated Tdew. Hourly average measurements of Rg and WS were more variable. We concluded that the PWS we selected will provide adequate values of rainfall and other weather variables to meet our goal of evaluating dryland cotton lint yield per unit rainfall.

Saline playas on the Southern High Plains are almost always located on large cattle ranches but they are of limited value to the herds of cattle grazing around their outer margins. Saline playas are often without water for extended periods and, after inundation, they experience considerable evaporative loss leading to hypersaline conditions. The primary goal of this study was to develop a quantitative method that combines the transitory nature of playa lakes and the variability of salinity into a set of parameters that can be used to compare playas or other surface water sources. Regarding water quality, a variable was developed that describes the fraction of observations with salinity levels below the salt tolerance threshold for cattle. With regard to water availability, water depth measurements were used to compute the fraction of time that a playa contains water. These two variables are combined to form a new variable that represents the fraction of time that water is both available and of acceptable quality. To demonstrate the utility of this method, data was collected at Yellow Lake, a large saline playa located on the Yellow House Ranch northwest of Lubbock, Texas. Results suggest that the playa contained water 50.8% of the time over a five-year period but the fraction of water samples with acceptable salinity was only 6.5%. The resulting fraction of time that water was both available and of acceptable quality was only 3.3%. This technique could be used to compare other ephemeral surface water sources in the region.

Abstract Beneath the high plains of the Llano Estacado lies the southern extension of the Ogallala aquifer, which provides a key source of groundwater for the region. Along the eastern fringes of the Llano Estacado one can find numerous natural springs that discharge from the Ogallala formation and provide a valuable source of freshwater. Large-scale irrigation has altered hydrological conditions, which has influenced the flow of springs along the eastern escarpment. In late 2012, the author began a study of one such spring located at Silver Falls in Blanco Canyon, east of Crosbyton, Texas. The goal was to monitor the discharge of this naturally flowing spring over a period of many years to establish temporal patterns. Measurements of spring flow rates over a seven-year period did not show an appreciable reduction associated with the depletion of the Ogallala aquifer; however, discharge was found to follow a seasonal pattern of declining flow during the summer followed by a recovery starting in late fall and reaching maximum discharge during winter and early spring. Whereas seasonal variations of spring discharge can be measured precisely, the cause of these seasonal patterns is less certain. It is likely that the combined effects of seasonal groundwater extraction for irrigation and the growth and transpiration of natural vegetation contribute to the observed seasonal patterns of groundwater discharge at Silver Falls.

Rainfall samples collected on the high plains of West Texas exhibit a high degree of variability with respect to the concentration of dissolved solids. That such variations should occur is to be expected, but there remains some uncertainty regarding factors that influence the ionic composition of individual samples. Measurements often show a distinct decrease in concentration with increasing precipitation amount. The reason for this inverse relationship is not intuitively obvious; however, it can be explained from a theoretical perspective. A theory was proposed that describes the concentration of dissolved solids in a collected rainfall sample. The theoretical basis of the derived equation rests upon fundamental principles of conservation of fluid volume and conservation of mass. This equation, which provides valuable insight into the process, suggests that if the rain sampling tube is absolutely clean at the start of a rain event, then the rainfall sample will not be altered by its collection and, therefore, will provide a true measure of rainfall chemistry. However, if windblown dust or other impurities are allowed to deposit in the rain gauge prior to or during the early stages of a rain event, then the concentration of dissolved solids can be very large for small sample volumes and not at all representative of the true concentration within the rain cloud. Results suggest that impurities in the rain sample can be appreciably diluted by the addition of relatively pure rainwater such that the concentration will asymptotically approach the true concentration as the rainfall sample volume increases.

Multiseed (msd) mutant sorghum [Sorghum bicolor (L.) Moench] lines with greatly increased seed numbers were developed. It was originally thought that the msd trait could increase grain yield several times in comparison with the wild type from which the mutant was derived. However, in a small plot trial, msd seed yield decreased when compared to the parent line. Herein we report results that msd seed yield remained either unchanged or slightly increased in comparison to the parent line. We suggest that attempts to measure msd sorghum seed yield were complicated due to systematic errors associated with the post-harvest processing methods, including threshing and pneumatic winnowing equipment that was used for harvest. That is, seed recovery and seed loss from individual panicles were affected by the post-harvest processing. When evaluating sorghum grain yield of types with different seed sizes, threshing and seed cleaning harvesting methods should be optimized for each sorghum line.

An existing Purdue-type rainfall simulator (RFS) was designed to be transported using a commercial flatbed trailer that was modified by cutting out a section of the wooden bed allowing the RFS to be positioned directly above the target area to measure soil erosion and water runoff. To allow water to pass through the trailer undisturbed, the axle of the trailer was removed and replaced with axle-free wheel hubs and springs. Additionally, a remote control mover rated for 2000 kg was incorporated in our design. The final result was a portable and mobile RFS that can be moved to fields using a trailer hitch and can be operated by two individuals. The cost of the hardware, not including the RFS, is $5300 (USD) and detailed design plans are available.

The Ogallala Aquifer extends beneath eight states in the Great Plains region of North America. It stretches from Texas to South Dakota and is among the largest aquifers in the world. In Texas, extraction of groundwater, primarily for cropland irrigation, far exceeds recharge resulting in a significant decline of the water table. In the Texas High Plains, this decline prompted restrictions set by a local water conservation agency in 2009 stating that in 50 years about 50% of the saturated thickness of the Ogallala Aquifer should be preserved. However, this restriction only addressed the quantity and not the quality of the remaining water. The quality of water extracted from the Ogallala Aquifer has been observed to change over time, especially over the length of a crop’s growing season. We measured water quality over a three-year period using an electrical conductivity sensor and measured depth to water at 20 locations across five counties in the Texas High Plains. Results show that when wells are actively pumping, water quality can change in complex and unpredictable ways. In some cases, water quality declined and in others water quality improved. This result has prompted us to further investigate the mechanisms involved in observed seasonal water quality changes.

Study region: The Llano Estacado is a vast elevated plain located at the southern end of the Great Plains of North America. The Llano Estacado region is favorably situated above the southernmost extension of the Ogallala Aquifer, which provides groundwater for a highly productive irrigated agricultural system. Study focus: A method was developed to compute the average deviation of the groundwater level from a nonstationary annual-average water level. New hydrological insights for the region: Groundwater is pumped from the Ogallala Aquifer during each growing season, which induces seasonal and long-term changes in observed groundwater levels. Recorder wells, maintained by the Texas Water Development Board, track these changes and provide a wealth of hydrologic data. Of special interest here are seasonal water-level perturbations induced by nearby actively pumped wells. Groundwater levels are observed to follow a regular pattern of declining water levels during the growing season followed by a recovery after irrigation systems are shut down. In areas with limited groundwater, farmers may shut off irrigation systems when soil moisture is adequate or when the supply of available water becomes critically low. As a result, one can often detect periods during the growing season when irrigation is paused and the water table is allowed time to partially recover. Such hydrographic deviations appear to correlate closely with periods of abundant rainfall. In areas where groundwater supplies are more plentiful, irrigation breaks are less evident. This suggests that farmers with adequate groundwater may be less inclined to shutdown irrigation systems to conserve water despite adequate rainfall.

Aeolian transport is driven by aerodynamic surface stress imposed by turbulent winds in the Earth’s atmospheric boundary layer (ABL). ABL regime is influenced by stratification, which can either enhance or suppress production of turbulence by shear associated with the vertical gradient of streamwise velocity. During the day and night, surface heat fluxes induce a negative (unstable) and positive (stable) vertical gradient of potential temperature, respectively, which modifies the role of buoyancy in turbulence production. During the brief morning and evening transition periods, the vertical gradient of potential temperature vanishes (neutral stratification). The Monin–Obukhov similarity theory describes how the vertical gradient of streamwise velocity varies with stratification. Simultaneous field measurement of wind speed and aeolian activity were obtained over a 218-day period on a bare, sandy surface on the high plains of the Llano Estacado region of west Texas. Wind speed was measured at a height of 2m with a propeller-type anemometer and aeolian activity was measured at the surface with a piezoelectric saltation sensor. We have used the wind speed measurements within the framework of the Monin–Obukhov similarity theory to estimate “typical” shear velocity, u∗, of the ABL as stratification is varied (characterized with the stability parameter). This approach results in a color flood contour of u∗ against time of day and stability parameter: the procedure demonstrates that aeolian activity is most likely to occur during the day, when buoyancy acts in conjunction with mechanical shear to increase u∗.

Numerous complex geomorphic and hydrologic factors have been identified that control dust emissions from playas, yet there are few measurements of dust emissions from playas during drought, which is assumed to enhance emissions, or during low-emission seasons. We used the PI-SWERL (Portable in situ Wind Erosion Laboratory) to measure dust emission potential at Yellow Lake, a saline playa in West Texas, USA, during the drought of 2011. Direct aeolian entrainment of dust occurred primarily on supply limited surfaces consisting of mud-cracked surfaces as well as crusts containing halite, thenardite, and gypsum. High-magnitude, low duration peaks in dust emissions occurred over parts of the playa underlain by shallow groundwater (<1 m) where conditions encouraged the crystallization of efflorescent salts. In contrast, surfaces characterized by loose sand-sized aggregates produced sustained dust emissions two to three orders of magnitude higher than the playa surface because aggregates broke apart during saltation. Prolonged drought at Yellow Lake will significantly change the frequency and type of dust emissions. We propose that a similar scenario characterizes dust production at many hydrologically similar playas. More research is needed to assess the impacts of changing groundwater levels on dust emissions in the context of extended drought and anthropogenic climate change. (C) 2016 Elsevier Ltd. All rights reserved.

In June 2015 the TRMM satellite came to its end. The 17+ year of mission data that it provided has proven a valuable asset to a variety of science communities. This 17+ year data set does not, however, stagnate with the end of the mission itself. NASA/JAXA intend to integrate the TRMM data set into the data suite of the GPM mission. This will ensure the creation of a consistent, intercalibrated, accurate dataset within GPM that extends back to November of 1998. This paper describes the plans for incorporating the TRMM 17+ year data into the GPM data suite. These plans call for using GPM algorithms for both radiometer and radar to reprocess TRMM data as well as intercalibrating partner radiometers using GPM intercalibration techniques. This reprocessing will mean changes in content, logical format and physical format as well as improved geolocation, sensor corrections and retrieval techniques.

Declines in Ogallala aquifer levels used for irrigation has prompted research to identify methods for optimizing water use efficiency (WUE) of cotton (Gossypium hirsutum L). In this experiment, conducted at Lubbock, TX, USA in 2014, our objective was to test two canopy temperature based stress indices, each at two different irrigation trigger set points: the Stress Time (ST) method with irrigation triggers set at 5.5 (ST_5.5) and 8.5 h (ST_8.5) and the Crop Water Stress Index (CWSI) method with irrigation triggers set at 0.3 (CWSI_0.3) and 0.6 (CWSI_0.6). When these irrigation triggers were exceeded on a given day, the crop was deficit irrigated with 5 mm of water via subsurface drip tape. Also included in the experimental design were a well-watered (WW) control irrigated at 110% of potential evapotranspiration and a dry land (DL) treatment that relied on rainfall only. Seasonal crop water use ranged from 353 to 625 mm across these six treatments. As expected, cotton lint yield increased with increasing crop water use but lint yield WUE displayed asignificant (p ≤ 0.05) peak near 3.6 to 3.7 kg ha−1 mm−1 for the ST_5.5 and CWSI_0.3 treatments, respectively. Our results suggest that WUE may be optimized in cotton with less water than that needed for maximum lint yield.

Hourly dust data was collected in Lubbock, Texas, from January 1, 2003, to January 1, 2008. Diurnal patterns of dust concentration were computed by averaging hourly values associated with a given time of day for all days within the 5-yr sampling period. Results suggest that the overall diurnal pattern is characterized by relatively high dust concentrations during the day and relatively low values at night and in the early morning. Diurnal patterns of blowing dust are influenced by daily variations of key climatic factors. Generally, one finds relatively strong winds during the day and lighter winds at night. The morning increase in wind speed is associated with the rising sun, which produces thermal instability and enhances the mixing of high momentum winds from the upper levels of the atmosphere to the surface layer. Solar radiation can also reduce the critical threshold by drying the soil surface. Diurnal patterns of blowing dust were also computed separately for each of the four seasons. The most conspicuous change of the diurnal pattern occurred in the summer where the difference between peak afternoon values and early morning values was considerably less than that of other seasons.