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A seasonal groundwater model was developed to simulate fluxes and head distributions with periodic boundary conditions within the San Pedro Riparian National Conservation Area (SPRNCA) in southeastern Arizona. This model incorporated a seasonal approach for the period 1940-1995. Two years were used to simulate streamflow, 1990 and 1995. The model, as currently calibrated, does not accurately reproduce observed baseflow conditions in the San Pedro River and simulates an exaggerated effect of retiring irrigation within the SPRNCA. The model simulated increased baseflows while the observed baseflows declined at the USGS Charleston stream gage, though increases in baseflow contributions between Hereford Bridge and Lewis Springs have been reported. The original (Corell, et al., 1996) model and the seasonal transient model suffer from over- estimation of discharge from the floodplain aquifer to the San Pedro river, as well as errors in the seasonal transient model's simulation of riparian ET, and seasonal variations in stream conductance. These problems precluded the seasonal transient model from replicating the observed baseflows in the San Pedro river at the Charleston bridge, however, the results of the simulation are thought to be qualitatively indicative of changes in the flow system resulting from the retirement of irrigated agriculture in the San Pedro Riparian National Conservation Area. Possible sources for this problem include replacement of irrigation stresses by the expansion of cones of depression more distant from the river, overestimation of mountain front recharge, poor baseflow estimates and evapotransipration calculations from the stream gages at Charleston and Palominas, and the effects of a recently discovered silt -clay body that may dampen the speed of the rivers response to changes in stress. Additional efforts to re- calibrate the model, taking these areas into account, should provide better simulated baseflow values of the observed data.

MRDV / Institute for Rural Development / See the attached abstract below

Call number: LD2668 .T4 1985 M49 / Master of Science

The level of future agricultural production in Central Arizona depends upon the availability of land and water, the cost of water, and opportunities to grow crops yielding high returns per acre-foot of water. Suitable land is abundantly available but groundwater appurtenant to these lands is becoming increasingly costly. Opportunities to grow high-value crops are subject to the vagaries of commodity markets and government programs. This study estimates the direction and magnitude of expected agricultural adjustments in response to a declining land and water base, increasing water costs, and intra-county transfer of cotton allotments. The study region, encompassing all areas of Maricopa County relying solely or primarily upon groundwater for irrigation, is divided into two water resource areas. Area A has low-cost, poor quality water and only cotton for a high-value crop. Area B has highcost, good quality water and cotton, vegetables, and citrus for highvalue crops. Nine representative farm models are developed characterizing the structure of the agricultural sector of the economy in these two areas. Data for ten crops grown by these nine farm size groups are incorporated into linear programming models to make projections for 18 water situations distinguished on the basis of source, availability, and cost of water. Projections are made for the period 1967 to 2015. Projected adjustments show over 20 percent declines in land and water use and a 13 percent decline in net revenues over variable costs of production for the study region by 2015. These declines occur due to a loss of 68,000 acres of land to urban uses, and the abandonment of lowvalue crops made unprofitable by rising water costs. Declines in resource use and incomes are mitigated by a 10,000 acre increase in cotton production due to transfers of allotments from an adjacent region experiencing greater losses of land and water to urban uses. Projections by water resource area and water situation show 7 and 13 percent decreases in land and water use and a 7 percent increase in net revenues over variable costs for Area A. This divergent movement of resource use and revenues occurs because a 64 percent increase in cotton acreage offsets substantial reductions in sorghum and safflower acreages. Area B projections show approximately a 30 percent reduction in land and water use and a 23 percent reduction in net revenues over variable production costs. These reductions occur because all resources lost to urban uses come from this area and large acreages of low-value crops go out of production due to rising water costs. Only small acreages of short staple cotton allotments are transferred to Area B farms because Area A farmers can afford to pay more for surplus allotments. Area B experiences a net loss of cotton acreage because long staple allotments are transferred to Area A ferns when water costs make this variety of cotton unprofitable in Area B water situations. Projections by water situation within the two water resource areas vary from increases in resource use and net incomes to large decreases. The agricultural sector of Maricopa County expands until 1960, then enters a stage of decline, accelerated by large losses of land and water resources to urban uses in one irrigation district with adequate supplies of low-cost water. A comprehensive land use plan with zoning restrictions preventing urbanization of low-cost water areas would help maintain agricultural resource use and incomes at levels higher than will otherwise occur. Such a plan would also help maintain the quality of Che urban environment in Maricopa County.

Bibliography: leaves 146-153. This thesis analyses factors influencing farmers use of groundwater pump irrigation in Lombok, Indonesia. It aims to identify the determinants of the speed of technology adoption, to identify factors affecting the levels of water use and to estimate the state of water use by comparing the actual water use to the estimated optimal water use.

This thesis examines the local waterscapes of two smallholder irrigation farming systems in the dry lands of East African in a context of socio-ecological changes. It focuses on three aspects: institutional arrangements, gender relations and landscape investments.  This thesis is based on a reflexive analysis of cross-cultural, cross-language research, particularly focusing on the role of field assistants and interpreters, and on member checking as a method to ensure validity. Flexible irrigation infrastructure in Sibou, Kenya, and Engaruka, Tanzania, allow farmers to shift the course of water and to extend or reduce the area cultivated depending on seasonal rainfall patterns. Water conflicts are avoided through a decentralized common property management system. Water rights are continuously renegotiated depending on water supply. Water is seen as a common good the management of which is guided by mutual understanding to prevent conflicts through participation and shared information about water rights. However, participation in water management is a privilege that is endowed mostly to men. Strict patriarchal norms regulate control over water and practically exclude women from irrigation management. The control over water usage for productive means is a manifestation of masculinity. The same gender bias has emerged in recent decades as men have increased their engagement in agriculture by cultivating crops for sale. Women, because of their subordinated position, cannot take advantage of the recent livelihood diversification. Rather, the cultivation of horticultural products for sale has increased the workload for women who already farm most food crops for family consumption. In addition, they now have to weed and harvest the commercial crops that their husbands sell for profit. This agricultural gender divide is mirrored in men´s and women´s response to increased climate variability. Women intercrop as a risk adverting strategy, while men sow more rounds of crops for sale when the rain allows for it. Additionally, while discursively underestimated by men, women´s assistance is materially fundamental to maintaining of the irrigation infrastructure and to ensuring the soil fertility that makes the cultivation of crops for sale possible. In sum, this thesis highlights the adaptation potentials of contemporary smallholder irrigation systems through local common property regimes that, while not inclusive towards women, avoid conflicts generated by shifting water supply and increased climate variability. To be able to assess the success and viability of irrigation systems, research must be carried out at a local level. By studying how local water management works, how conflicts are adverted through common property regimes and how these systems adapt to socio-ecological changes, this thesis provides insights that are important both for the planning of current irrigation schemes and the rehabilitation or the extension of older systems. By investigating the factors behind the consistent marginalization of women from water management and their subordinated role in agricultural production, this study also cautions against the reproduction of these discriminatory norms in the planning of irrigation projects. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p><p> </p>

A risk analysis of drought and an assessment of irrigation requirements were ascertained for a wheat (Triticum aestivum L.) crop in Parana, Brazil, using 28 years of historical weather data. Two soil moisture models, The Versatile Soil Moisture Budget (VB4) and SWACROP models, were compared using data from six wheat cropping periods. The models showed good performance in predicting soil moisture contents, but SWACROP underpredicted soil evaporation and runoff, and VB4 did not separate evapotranspiration into its components. Therefore, a new soil moisture model was proposed. In the new model, a Darcy type equation was used to calculate fluxes in the soil profile, and inputs of daily rainfall and potential evapotranspiration were partitioned during the day using simple disaggregation methods. Crop growth input parameters, interacting with weather and soil inputs, were used to calculate a detailed output of the water balance components. The validation of the model showed predictions of soil water contents and evapotranspiration in close agreement with field data. / A crop yield model based on the stress day index approach was selected from an evaluation of seven crop-water production functions using wheat field data. This model was combined with the soil moisture model to assess risks of drought during the establishment and development of non-irrigated wheat crops with different planting dates. Irrigation management strategies were simulated to identify net system delivery capacities and application frequencies that promote maximum yield with minimum requirements of water. Yield reductions in non-irrigated wheat due to water stress varied between 16%, for early plantings, to 50%, for late plantings. Maximum yields with minimum applied water was obtained by the use of low intensity (5 to 10 mm) and frequent (3 to 5 days) irrigations. System delivery capacity requirements varied from 1.5 to 3.0 mm/day, according to planting dates.