Integrating Groundwater Observations with Models of Soil-Water Dynamics to Examine Recharge Patterns through Glacial Sediments in a Humid Continental Climate

Poster presented at American Geophysical Union meeting in 2015.Understanding the timing and magnitude of shallow groundwater recharge is critical for determining water balance and analyzing aquifer sensitivity for water resource planning. We analyzed data from six hydrometeorological monitoring stations using HYDRUS 1D to achieve physically based estimates of water-table recharge in various glaciated terrains in Indiana (USA). The models simulated runoff, root-water uptake, and flow through heterogeneous soil profiles to quantify water flux at the water table. Calibration by inverse modeling of data collected in 2013 yielded optimized hydraulic parameters that allowed accurate simulation of observed soil moisture (RMSE generally within 3%). The model validation period confirmed accurate simulation of soil moisture as well as correspondence between modeled recharge and observed water-table fluctuations. Additional modelling over a three-year study period indicated that diffuse water-table recharge in the region can be reasonably approximated as 35% of precipitation, but interannual and monthly variability can be significant depending on the glacial setting and pedological development. Soil parent material and horizon characteristics have a strong influence on average annual recharge primarily through their control on Ks, with clay-rich till parent materials producing values as low as 16% and coarse-grained outwash parent materials producing values as high as 58% of precipitation. The combined modelling and monitoring data reveal distinct seasonality of recharge, with most recharge occurring in the winter (seasonal mean of all sites was 66% of precipitation) and lesser but interannually stable amounts in the spring (44%), summer (13%), and autumn (16%). This ongoing research underscores the value of combining vadose zone characterization with hydrometeorological monitoring to more effectively represent how surface energy and moisture budgets influence the dynamics of surface water-groundwater interactions

Relationships between gastrointestinal permeability, heat stress, and milk production in lactating dairy cows

ABSTRACT: Heat stress (HS) is a global issue that decreases farm profits and compromises animal welfare. To distinguish between the direct and indirect effects of HS, 16 multiparous Holstein cows approximately 100 DIM were assigned to one of 2 treatments: pair fed to match HS cow intake, housed in thermoneutral conditions (PFTN, n = 8) or cyclical HS (n = 8). All cows were subjected to 2 experimental periods. Period 1 consisted of a 4 d thermoneutral period with ad libitum intake. During period 2 (P2), the HS cows were housed in cyclical HS conditions with a temperature-humidity index (THI) ranging from 76 to 80 and the PFTN cows were exposed to a constant THI of 64 for 4 d. Dry matter intake of the PFTN cows was intake matched to the HS cows. Milk yield, milk composition, rectal temperature, and respiration rate were recorded twice daily, blood was collected daily via a jugular catheter, and cows were fed twice daily. On d 3 of each period, Cr-EDTA and sucralose were orally administered and recovered via 24 h total urine collection to assess gastrointestinal permeability. All data were analyzed using the GLIMMIX procedure in SAS. The daily data collected in P1 was averaged and used as a covariate if deemed significant in the model. Heat stress decreased voluntary feed intake by 35% and increased rectal temperature and respiration rate (38.4°C vs. 39.4°C and 40 vs. 71 respirations/min, respectively). Heat stress reduced DMI by 35%, which accounted for 66% of the decrease in milk yield. The yields, and not concentrations, of milk protein, fat, and other solids were lower in the HS cows on d 4 of P2. Milk urea nitrogen was higher and plasma urea nitrogen tended to be higher on d 3 and d 4 of HS. Glucose was 7% lower in the HS cows and insulin was 71% higher in the HS cows than the PFTN cows on d 4 of P2. No difference in lipopolysaccharide-binding protein was observed. Heat stress cows produced 7 L/d more urine than PFTN cows. No differences were detected in the urine concentration or percentage of the oral dose recovered for Cr-EDTA or sucralose. In conclusion, HS was responsible for 34% of the reduction of milk yield. The elevated MUN and the tendency for elevated plasma urea nitrogen indicate a whole-body shift in nitrogen metabolism. No differences in gastrointestinal permeability or lipopolysaccharide-binding protein were observed. These results indicate that, under the conditions of this experiment, activation of the immune system by gut-derived lipopolysaccharide was not responsible for the decreased milk yield observed during HS