The Control, Development and Utilization of the Missouri River and its Tributaries

The speakers at this conference were Professors Condra, Caldwell, Stout, Phillips, Bengtson, and Gov. George L. Sheldon, with Dean Charles E. Bessey presiding. The principal object of the meeting was to make known reliable information in regard to the Missouri river, concerning which there is widespread interest and in some instances a tendency to magnify the future possibilities of the river. This paper is an account of the conference. It gives some of the thoughts that were emphasized at the symposium, reciting the facts as they were given by those who have investigated the respective phases of the theme. GEOGRAPHIC CONDITIONS IN THE MISSOURI RIVER BASIN. BY G. E. CONDRA EARLY NAVIGATION ON THE MISSOURI RIVER. BY H. W. CALDWELL THE RELATIONS OF POWER AND IRRIGATION AT THE HEADWATERS OF THE MISSOURI TO FLOODS IN THE LOWER COURSES OF THE RIVER BY O. V. P. STOUT THE RELATIONS OF FORES\u27fS TO RUN-OFF WATER. BY F. J. PHILLIPS MEANDERS OF THE MISSOURI RIVER AND THEIR EFFECTS. BY. N. A. BENGTSON WAYS AND MEANS. GOV. GEO. L, SHELDON

A Model for Estimating Demand for Irrigation Water on the Texas High Plains

With rapidly changing conditions in production agriculture, the need for highly flexible and quickly applicable methods of analysis is emphasized. The purpose of this study was to develop such a model for a homogeneous production region in the Texas High Plains. A linear programming model was constructed whereby crop or input prices are readily adjustable. In addition, limitations on quantities of inputs available can easily be evaluated. The model contains cotton, grain sorghum, corn, wheat and soybeans. Inputs that can be evaluated include irrigation water, natural gas, diesel, nitrogen fertilizer and herbicides. The primary focus of this work was to estimate the demand for irrigation water in the study area. The model was applied using alternative crop prices and input prices. Assuming average crop prices, current input prices and only variable costs of production, as the price of water was increased wheat shifted from irrigated to dryland production, then grain sorghum, cotton, corn and soybeans, in that order. The price of water was $71.75 per acre foot plus current pumping cost when all land shifted to dryland production. The same analysis, except variable and fixed costs both included, gave similar results relative to the sequence of crops that shift to dryland production as the price of water was increased. However, the shifts occurred at much lower water prices; i.e., at$24.47 per acre foot plus current pumping costs, all land had shifted to dryland production. This suggests that over the long run, irrigation in the Texas High Plains is quite sensitive to the price of energy used in pumping water. Further, there are strong implications relative to farmer's "ability to pay" for water imported to the High Plains from other regions. In this report, several scenarios including low, high and average crop prices and average and high input prices were evaluated

The Impact of Energy Shortage and Cost on Irrigation for the High Plains and Trans Pecos Regions of Texas

The High Plains and Trans Pecos regions of Texas are semi-arid crop production regions located in the western part of the state. Relatively low levels of rainfall are supplemented by irrigation from groundwater supplies. These regions produced 51 percent of the cotton, 42 percent of the grain sorghum, and 48 percent of the wheat produced in Texas in 1974 (Texas Crop and Livestock Reporting Service). Considering only irrigated production these percentages were 75, 85, and 91 percent of Texas irrigated crop production for cotton, grain sorghum and wheat respectively. The importance of the High Plains and Trans Pecos regions to Texas crop production are not limited to these three crops, however, these statistics do serve to illustrate the significance of these regions in the Texas agricultural economy. While it is easily seen that the majority of irrigated production (for the crops mentioned) in Texas occurs in these regions, it should be noted that the importance of irrigation in the High Plains and Trans Pecos regional economies is much greater than these statistics show. On the High Plains 86 percent of the cotton, 90 percent of the grain sorghum, and 75 percent of the wheat produced in 1974 was harvested from irrigated acreage. Rainfall is somewhat less in the Trans Pecos region and 100 percent of the production of these crops was under irrigation (Texas Crop and Livestock Reporting Service). More than 60 percent of the value of agricultural crops in Texas is produced on irrigated land (Knutson, et.al.). Thus, the crop production of these regions is vitally important to the Texas and respective regional economies. Crop yields are heavily dependent on groundwater irrigation and extremely sensitive to any factor which may affect the availability or cost of irrigation water. Availability and price of fuel used in pumping groundwater are the critical factors which directly affect the availability and cost of irrigation water. About 39 percent of the energy used in Texas agriculture in 1973 was utilized in pumping water, compared to 18 percent used in machinery operations. Of this irrigation fuel, 76 percent was natural gas, the majority of which was consumed in the High Plains (Coble and LePori). Current supplies and reserves of natural gas have reached critically low levels in recent years and producers in the High Plains and Trans Pecos regions are faced with possible curtailments of, and certain price increases for their irrigation fuel (Patton and Lacewell). The threat of possible curtailment of fuel supplies during the irrigation season imposes greatly increased risk to irrigated crop production since curtailment of natural gas supplies during a critical water use period would significantly reduce yields (Lacewell). This threat would also increase financial risk and restrict availability of credit. Continued price increases for natural gas will increase costs of pumping irrigation water and hence the costs of irrigated crop production (Patton and Lacewell). The Ogalalla aquifer underlying the High Plains and many of the alluvium aquifers underlying the Trans Pecos are exhaustible; i.e., there is a negligible recharge from percolation and other sources. Therefore, even with unchanged natural gas prices, these groundwater supplies are being "economically" exhausted over time as pumping depth increases. Increases in fuel prices will lead to reduced groundwater pumpage and result in less groundwater being economically recoverable. Although life of the physical supply will be exhausted, a greater quantity of groundwater will be economically unrecoverable for irrigation without significant product price increases

Polymorphism in Gag Gene Cleavage Sites of HIV-1 Non-B Subtype and Virological Outcome of a First-Line Lopinavir/Ritonavir Single Drug Regimen

Virological failure on a boosted-protease inhibitor (PI/r) first-line triple combination is usually not associated with the detection of resistance mutations in the protease gene. Thus, other resistance pathways are being investigated. First-line PI/r monotherapy is the best model to investigate in vivo if the presence of mutations in the cleavage sites (CS) of gag gene prior to any antiretroviral treatment might influence PI/r efficacy. 83 patients were assigned to initiate antiretroviral treatment with first-line lopinavir/r monotherapy in the randomised Monark trial. We compared baseline sequence of gag CS between patients harbouring B or non-B HIV-1 subtype, and between those who achieved viral suppression and those who experienced virological failure while on LPV/r monotherapy up to Week 96. Baseline sequence of gag CS was available for 82/83 isolates; 81/82 carried at least one substitution in gag CS compared to HXB2 sequence. At baseline, non-B subtype isolates were significantly more likely to harbour mutations in gag CS than B subtype isolates (p<0.0001). Twenty-three patients experienced virological failure while on lopinavir/r monotherapy. The presence of more than two substitutions in p2/NC site at baseline significantly predicted virological failure (p = 0.0479), non-B subtype isolates being more likely to harbour more than two substitutions in this specific site. In conclusion, gag cleavage site was highly polymorphic in antiretroviral-naive patients harbouring a non-B HIV-1 strain. We show that pre-therapy mutations in gag cleavage site sequence were significantly associated with the virological outcome of a first-line LPV/r single drug regimen in the Monark trial

Surveillance of Transmitted Antiretroviral Drug Resistance among HIV-1 Infected Women Attending Antenatal Clinics in Chitungwiza, Zimbabwe

The rapid scale-up of highly active antiretroviral therapy (HAART) and use of single dose Nevirapine (SD NVP) for prevention of mother-to-child transmission (pMTCT) have raised fears about the emergence of resistance to the first line antiretroviral drug regimens. A cross-sectional study was conducted to determine the prevalence of primary drug resistance (PDR) in a cohort of young (<25 yrs) HAART-naïve HIV pregnant women attending antenatal clinics in Chitungwiza, Zimbabwe. Whole blood was collected in EDTA for CD4 counts, viral load, serological estimation of duration of infection using the BED Calypte assay and genotyping for drug resistance. Four hundred and seventy-one women, mean age 21 years; SD: 2.1 were enrolled into the study between 2006 and 2007. Their median CD4 count was 371cells/µL; IQR: 255–511 cells/µL. Two hundred and thirty-six samples were genotyped for drug resistance. Based on the BED assay, 27% were recently infected (RI) whilst 73% had long-term infection (LTI). Median CD4 count was higher (p<0.05) in RI than in women with LTI. Only 2 women had drug resistance mutations; protease I85V and reverse transcriptase Y181C. Prevalence of PDR in Chitungwiza, 4 years after commencement of the national ART program remained below WHO threshold limit (5%). Frequency of recent infection BED testing is consistent with high HIV acquisition during pregnancy. With the scale-up of long-term ART programs, maintenance of proper prescribing practices, continuous monitoring of patients and reinforcement of adherence may prevent the acquisition and transmission of PDR