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Tim Thanks for the brief run down on your experiance. As for my experiance, I have none. I have only recently become certified to use the neutron probe. The Department has had one since, I believe, the 1970's. I have looked at data that was gathered with the probe. In California water transfers (the selling of water) are becoming an increasingly popular way of increasing urban water supply reliability. Most of these transfers are from agriculture to urban users. Evapotranspiration numbers (unit use by crop by area) that we have were developed in the 1970's mostly from lysmeter data. Although I believe our numbers are still good things have changed. The Department is planning to update these numbers. I would like to use the neutron probe for this update. Will time and money allow this? I don't know at this time. When the numbers were developed they were used as a planning and irrigation tool. In todays world dollars are being attached to unit use numbers for water transfers. It is my opinon that we now need to "tighten" these numbers because of how they are now being used. And that is why I am interested in neutron probes. Thanks dean --- Begin Included Message --- On Tue, 15 Oct 96 09:55: 7 PDT dreynold@cd-eso.water.ca.gov wrote: > From: dreynold@cd-eso.water.ca.gov> Date: Tue, 15 Oct 96 09:55: 7 PDT > Subject: Neutron Probes > To: SOWACS@aqua.ccwr.ac.za > > Tim, > > What is your experiance with Neutron Probes? > > 1. During the late 1980's we ran an irrigation scheduling service for UK farmers using the neutron probe and a soil water balance model. We were visiting farms once every two weeks. The general experience was good, however, we dropped the probe (not literally!) as we found that the model alone gave adequate accuracy at a fraction of the cost. 2. I spent a period in N E Nigeria, part of which included a study of the soil water balance of millet-cowpea intercropping systems. This was based largely on neutron probe measurements. 3. I ran a training course in Indonesia on the use of the neutron probe for soil water studies in semi-arid environments. My overall opinion of the neutron probe is that it is still the best thing that we have for repeatedly measuring soil water content at a large number of points at reasonable cost. Capacitance / TDR approaches are lovely for a few places, but as the instrumentation has to be replicated at every point the cost escalates rapidly. I hope that one-day we will be able to ditch the neutron probe as it is potentially hazardous, but I haven;t seen anything yet to replace it. What is your experience? Tim --------------------------------------------------------------------- Tim Hess Department of Water Management Silsoe College Cranfield University Silsoe Tel (0)1525 863292 Bedford, MK45 4DT Fax (0)1525 863000 UK e-mail t.hess@cranfield.ac.uk http://www.cranfield.ac.uk/safe/people/thess.htm ---------------------------------------------------------------------- --- End Included Message --- ******************************************************** Dean Reynolds Associate Land and Water Use Analyst California Department of Water Resources 3251 S Street Sacramento, Ca. 95816 916-227-7602 916-227-7600 Fax dreynold@water.ca.gov